I use a 3 inch wide cotton strap from Levis. Slouching is the reason I use one, as I mentioned before because of my tall body. I sit in a chair with my back straight. My guitar weighs about 8.5 pounds and I don’t get uncomfortable with the wide strap (with OLD Schaller strap locks, I don’t like the new ones).
It’s gonna vary from person to person of course. Stands are neat for live performance, but standing up for hours on end without moving around is also not good for your feet and knees.
I much prefer to play standing up. My strap is short so the guitar position really doesn’t change when I sit vs when I’m standing, but I just feel more engaged when I’m assuming a good posture while playing. I also get restless sitting in one spot for too long. Whenever I practice, I’m not just standing in place; I’m continuously wandering around the room.
One more observation on my end:
For 25.5 scale guitars (e.g. strat), I definitely prefer to play them standing with a strap. When Playing a 25.5 sitting down (using either leg), there’s always something that feels “too far to one side” (either fretting or picking hand)
I also have a 22’5 guitar (squier Jazzmaster mini), which conversely is pretty comfortable sitting down, and a little weirder to play standing up.
So my current solution is:
Sitting down - > play the 22’5
Standing up → play the 25’5
Body shape, neck to body weight distribution and strap button locations affect ergonomics. I have a Prisma Sunset that wants to swing to the left of my body center; the left strap button is located near the 22nd fret and is not comfy on a strap. Then my telecaster has a strap button near the 16th fret, and is cozy on a strap.
Great question!! Claus is awesome… love that stand.
My practice sessions are hours… that would be tough for me but I think it’s really important to practice standing.