The way I see it, it depends on several factors.
-How one’s mind operates. For me, I found out, it’s easier to recall , say 7 notes of a particular key or scale than a bunch of different shapes-shapes are always different, the notes are always the same. On the other hand, being aware of the shapes-as many shapes as possible-gives me faster access to the notes I’m looking for. Does that make any sense?
-We’re talking about improvisation, but over what? One thing is imrovising over a one chord modal vamp, a totally different thing is improvising over Giand Steps. For me, the more complex it gets the more impossible is to get away with just knowing the shapes.
-Which musicans are one’s role models? The ones I admire the most, that inspire me to grab a guitar and trying to become better and better are guys that knew their stuff inside out. I aspire to that level, no only chops-wise but having that level of deep understanding of the craft. I want to be able to communicate with other instrumentalists, and to do that we need a common ground-that common ground is not the techincal peculiarities of our specific instruments, instead it’s music itself.
-Another factor is the need one might have to develop new shapes. Maybe the shapes we’ve been taught don’t work with our particular techincal-say, picking-idiosyncransies. Maybe I need to find a way to play that scale pattern or arpeggio or Pat’s (any of them) lick. The thing is, I need to know what is this thing I’m looking for so I can re-locate it, re-finger it and built a new shape around it, so it can work with, say, my preffered kind of pick slanting. Maybe it has happened to you guys, it sure has happened to me.
All the above, of course, is just my personal opinion. I’m aware, and have been a witness many many times, of people that need any of that to make important, powerful music.