The shortest possible answer is to be aware that both options are available, and to try both for the lick you are trying to play. Then, you can choose whatever gives you the best combination of : feeling good, sounding good, minimising mistakes!
A bit oversimplified, I know 
Thanks Tommo. I guess the hangup is that right now, 99% of the time it feels more comfortable to use the pinky - but that is likely only because this is how I have been playing for years.
I just wasn’t sure if there could be benefit into pouring a lot of time into practicing with P, I and R. Once my hand gets used to that, could that finger combination be physically faster than with the pinky?
Since I have seen so many of my favorite players using the ring finger, it really makes me wonder!
I’d suspect both are true. Tom Gilroy has written extensively about the choices and orders of fingers. I remember him noting that Paul Gilbert’s pinky, in relation to his ring, are closer in length that what we see in many players. Different scenario, but I know that aspect of physiology paired with the slanted posture he favors make things like index → ring → pinky very comfortable for him. I’m sure the choice of index → middle → pinky vs index → middle → ring is similar. To me the 2 versions don’t feel much different unless the patterns have multiple whole steps (or larger). Also, depending on where on the neck these happen I’ll make a different choice due to comfort. To me it’s all situational and personal.
You play some very challenging things, so I’d say if you’re getting good results, who cares what the other guys are doing lol!
I’ve read Tom’s work pretty extensively and he’s classed index → middle → pinky and index → middle → ring as functionally equivalent, so I doubt you’d get a speed boost by improving the one you’re not as strong on.
Are there particular phrases you’re trying to do where it seems like you have to use index → middle → ring, and you feel like that’s your bottleneck? Like playing 18 → 20 → 21 on the high E string…not enough room for me to use anything but I M R in that situation
@adamack I would just keep using your pinky and don’t worry about it. There may be times when a phrase feels better to use middle and ring for a 134 sequence (@Tom_Gilroy 's edc explains why) so if it feels comfortable in those situations, try it out.
Tom’s EDC’s don’t differentiate between 1 2 3 and 1 2 4 though. They just say to prefer it over 1 3 4. You and Paul Gilbert are infuriating outliers lol you seem to be able to hit top speed with 1 3 4…
Fair enough!
An idea that just popped into my mind is that you could try to get started on some 3 note-per-string scale patterns in the higher frets (say from the 12-14th fret onwards).
I noticed that the “one finger per fret rule” becomes pretty uncomfortable to follow up there, because the fingers feel all crammed together. So it’s an area of the neck where the 1-2-3 combination may feel more natural.
I might have to record a video for an example, but what I meant is that sometimes a whole note / half note sequence (like 5-7-8 on the fretboard) would be better suited as index / middle / ring instead of index / ring / pinky, even though you’re used to playing with I/R/P.
I just think it’s from not liking to stretch, for as long as I’ve been playing lol. I also don’t like to position shift, which is why the main thing I’ve been working on recently has been long scales with 3nps / 2nps mixes in order to not shift.
Gotcha. I think the OP mentions not the I/R/P issue, but that he prefers I/M/P in places some others opt for I/M/R
That’s how I interpreted it anyway.
I think that’s just another great example that great players (like you) often decide they don’t like the way something feels and opt for what works for them. On with life lol! My knee jerk reaction over the years was to always opt for the thing I was not as good at, thinking I’d come through on the other side more well rounded. That hasn’t worked out great for me lol Find an easier thing, do that thing is definitely the best way to progress.
Extremely helpful info, thanks! I really need to check out Tom Gilroy - had no idea someone had studied this subject in-depth.
And yes, Paul Gilbert is a great example of someone who uses the pinky a ton. He also uses index, ring, and pinky for whole step separations (5, 7, 9 for example) instead of what most people do - Index, Middle, and pinky. I do it Paul’s way, so it always made me feel better that there was a virtuostic-level player who did as well.
As for the results - most of the things I practice from these great players are nowhere close to being up-to speed, so this is one reason I have been questioning finger choice. I’ve wondered if the nature of the pinky has been holding me back from reaching their speeds in these phrases.
Here are some great resources on getting the most speed potential from the fretting hand
Just to be clear, in your original post you said you tend to use index middle pinky where others are using index middle ring, correct? And this is in the context of whole step followed by half step (i.e. 5 7 8 on the E string like @Pepepicks66 mentioned). I just want to make sure there wasn’t a typo 
Because you also mentioned for the whole step / whole step pattern (i.e. 5 7 9) you do it Paul’s way (index ring pinky). I’d absolutely expect a speed limit using index ring pinky.
Just like a tremolo is a test of how fast we can pick, a 3 finger ascending (or descending) roll is the faster we’ll be able to move our fretting hand. If you try the following, all hammer ons on one string repeatedly:
(With fingers index middle ring)
|-5-6-7-5-6-7-5-6-7-5-6-7-etc-|
OR
(with fingers index middle pinky)
|-5-6-8-5-6-8-5-6-8-5-6-8-etc-|
The idea in each case is to release (i.e. empty tension) the index as the middle frets. Release the middle as the (ring or pinky) frets. Release the (ring or pinky) as the cycle starts over again. This always gives each finger maximal time to recover and play again.
There are several things that can make this feel easier/harder. The position of your fretting hand and wrist (such as how parallel to the frets your fingers are, how bent/straight your wrist is), which string you are playing on, how wide the stretch is, whether your fingers are arched/straight in relation to what your personal hand at rest looks like. I’d say to try a variety of things until you find which parameters allow maximum speed. Once you establish a baseline, try it with the ‘other group’ of fingers and try to match the speed you achieved. Ideally index middle ring and index middle pinky will be equivalent. In most people, index ring pinky won’t have the stamina.
Lastly, I mentioned all hammers and ascending. But all hammers descending should have the same speed potential.
Good luck!
That’s more my current situation since I’m very vested in alternate picking everything, but when I first started, I pretty much brute forced alternate picking. It didn’t come naturally, at least not the hard lines. Trem more or less clicked pretty quickly because of metal, but I think I developed my alternate picking because there was no other kind of lead lines I wanted to do; arpeggios and legato never appealed to me, and since this was before CTC, I more or less “had” to develop some kind of DBX to play what I wanted.
Thanks, and yeah that will likely be the outcome. I have been trying to become comfortable with using the first 3 fingers, and making slight progress, but it doesn’t feel like something I will fully adapt to. So maybe my hand’s physiology is just better suited to using the pinky.
Yes thanks, good idea! The phrase I have been using to get comfortable with it is around the 5-7-8 area, so I may be pushing it now. I even encountered some pain and had to stop a few times.
I do seem to have much better success on the higher frets, so I will start getting more comfortable with it there first as you suggested - then see if I can swing the lower frets.
Yes - apologies for the confusion.
You got it 100% correctly though!
I should add - for the whole-whole progression (5-7-9), when on the lower frets I do use I, M, P. It was only in the past year or so that I got accustomed to this.
And thank you for the exercise! Very cool idea - something I never would have thought of. I will work this into my warmup segment.
Dumb question - when I switch to index, ring, pinky, am I staying with 5-6-8 to purposefully make an awkward bunchup? Or should I then go to 5-7-8?
No such thing as dumb questions!
So in Tom’s method of these fretting sequences, that ring/pinky combo is just flat out avoided if we want to reach the maximum speed. So let’s say you have to play something with a stretch like frets 1 3 4 on the Low E string…you’d do that with index middle pinky in the event that index middle ring doesn’t seem like you can stretch it. I’ve seen Yngwie do this even in places where he could probably easily make index middle ring work.
None of Tom’s research was saying “don’t you dare ever use the ring pinky combo in your playing ever” lol! It’s just that at the fastest possible speeds, it’s not going to hold up like either index middle ring or index middle pinky will. Ring/pinky are much more co dependent than our other fingers. It’s not quite as bad as string hopping is to our picking, but it’s got a similar type of “speed limitation”.
Oh wow thanks, that actually clarifies my original question then. That 1-3-4 on the Low E example was really illuminating!
Based on what you said about Tom’s research, it seems like there is benefit to me working on adjusting to Index, Middle, Ring for something like 5-7-8 than continuing to use Index, Ring, Pinky.
Maybe my reliance on ring/pinky has been a bit of a hinderance - it’s exciting to think that I could get a little more speed once I can adapt to the other fingering.
I would not be afraid to experiment, but your own results will dictate what to do. You might find I/R/P is faster for you, regardless of how much time you spend trying to make other fingerings work.
I think the ring is quite weak and not very flexible in terms of control. My own experience. Perhaps why the ring finger is the ring finger… the most vulnerable. We’ve got the least control of it.
Yeah, for sure. I’ll give it a couple months of working at it a little bit every day and see how things develop. Worst case, I will at least have some extra control over things at the end of it all. 
Many players avoid using the 4th finger right after or before the 3rd finger, since they are not 100% independent - if you stretch out your hand palms up, you can bend all fingers one by one except the pinky, which will drag along the third finger. If you play with a “blues vibrato”, you usually angle your fretting hand 45 degrees to the frets (less on the low strings, more on the high), which sometimes puts the pinky outside the fretboard. Piano players often prefer fingerings that avoids the succesion of pinky and ring finger.