Seat 4F is pretty good. Huge amount of stowage space under pair of F seats in front of you.
Seat 4B has "unlimited" legroom, but no stowage space (unless the passenger in 4A doesn't mind sharing).
Seat 4A has a huge amount of stowage space under the F class seat in front of it - I recently placed a very overstuffed backpack there instead of trying to cram it into the overhead. I'm 6'1" and had no trouble stretching my legs out all the way.