Are you bringing a desktop as well? If you are, then go with something portable. If not, then go with a desktop replacement because you likely won't be bring it to class that much. Most people don't unless it's a class requirement and you'll find that unless you're very disciplined or the lecture requires its use, you'll not be paying attention all that often
. Productivity wise, taking notes on a laptop sucks compared to a tablet. And in generally I can take notes by hand quicker than by typing (especially math and anything that requires diagrams, charts, figures, etc.)
I have a desktop and a laptop. The only time I use my laptop is to take home on relatively short breaks (i.e. everything but Winter break).