If you have good room acoustics, especially if you have treated reflections from the back wall, then a high back or low back chair/couch will both work reasonably well. If you have not treated your back walls, then a high back is likely to sound better (see next paragraph).
If you are trying to optimize SQ, then fabric is the best option. Leather/pleather will reflect more sound and you don't want that happening close to your head.
If you are trying to optimize SQ, then fabric is the best option. Leather/pleather will reflect more sound and you don't want that happening close to your head.