People ask these sorts of questions all the time, but it's absolutely subjective, it's different for EVERYONE. There are some who can't imagine less than a 15" or 17" laptop, others who think anything bigger than 13 might as well be a desktop.
Go play with them. Best Buy, Apple Store, Microcenter. You're talking about spending a grand so even if you have to drive an hour or so it may be worth it to go spend some time and play with them, check them out, see how they fit you.
If there was one clear winner Apple wouldn't sell so many shapes, sizes, and types of notebooks. Everyone is different, so figure out YOUR needs!