If I'm understanding you correctly, the APR DOES matter. Even if you pay on time, if you're making less than full payment, then you're paying the APR on the unpaid balance.
Someone warned against B of A, but I have -0- experience with them.
I think it's excellent that you're starting to build up a good credit history at your age.
As someone already mentioned, don't buy stuff with your card that you wouldn't have been able to afford if you didn't have a card.