I recently received a MKIII in .260. I have both stock skins and I do prefer the pistol grip to the thumbhole not for appearance but in function. I actually think the thumbhole grip looks better but I hate how it feels.
For my experience between those two I like both. But I had a lots of fan's in the range if I'm using thumbhole rather than pistol grip. Most people recognize right away that I'm using AI and dropped by and say "WOW!"
Thumbhole looks 100x better in my eyes.... but just feels too cramped for me. I had Viperskins on my 2 AICS, but they always looked a bit too unbalanced to my eye (front heavy).