It all depends on your build. Ideally, you want your leg from the knee up to balance out as best as possible with your leg from the knee down. For curvier girls, a bootcut is usually the way to go. For smaller and/or petite girls, a straight leg is probably the best bet, as hisbisus has already pointed out. If you're small, you don't want to get overwhelmed by too much fabric.
I think my favorites for thigh slimness are the first pair of Diesels I ever got, my Keate 81M's. It's partially the cut and partially the japanese denim, at least I think.