The best bats I've used have all had a rounded face. I'm not sure how rounded, and it could just be coincidence. Personally, in terms of looks, I quite like the flat face when looking at the side on profile, as it does make the bat look much more impressive, (Compare Icon F2 to Icon F7) but in terms of looking at it from the face, a mix between the two is my favourite. (F4.5) I don't mind a flat face, but it does give you more of a twisty feel when you hit off centre. Would always recommend you go with an oval handle when using a flat faced bat, as that helps prevent twist, and (from observations) also not to have it too concaved. (Changing grip relatively regularly also helps) I think a lot of it is in the mind, and what you feel most comfortable with, but the most noticeable difference in playability is the twist.