Please learn to think for yourself. It will be a valuable law school skill.
It also depends on how your workspace functions. What I mean by that is, how much you tend to sprawl out. I have a 14.1" from Dell but find in some classes, the space gets really cramped when you include your casebook and often times, your supplement, and get stuck with two people right next to you. Just some extra considerations, as those big lecture rooms, depending on class size, can get crowded, hot, and just overall miserable quick. If you can tolerate the weight though, and you're not walking everywhere, why not?
bus?? that might be a problem, actually. right now my car is my locker. i can't imagine having to take the bus with 2/3 case books and a 17" notebook. that would probably get old kinda quick.