I guess it all depends on the circumstances, like the kind of restaurant it is, and if I'm by myself or with others. If we're talking about a fast food place like McDonalds, I'd say it's a 50/50 split, since I might just go there to have something during a break at work, or bring it home if I have the day off. Any sort of restaurant (sans pizza places) that take some time to prepare your food, I almost always eat it there. I might bring home some leftovers, sure, but I'd rather avoid having to do any extra dishes if I don't have to.