I am interested in purchasing a MBP but not sure if I should go with a 13" or 15". I'll be using this computer in college next year so the computer will have to be portable. Is the MBP 15" worth the extra $200 over buying a MBP 13" or perhaps a MBP 13" with an external monitor? Also as a student, is the apple care recommended? Not really wanting to shell out money for an extended warranty. Thanks for any help.