I am debating between getting a 13" rMBP 3.0 GHz Dual-Core i7 or a 15" rMBP 2.8 GHz Quad-Core i7. Is there a noticible difference in speed between the two processors? I just want it for day-to-day use. I am a Third Grade Teacher and want to take it back and forth from home to my classroom. I always buy the fastest possible, but really prefer the 13" size. Unfortunately the 13" does not offer a Quad-Core configuration, so I am questioning if I should get a slightly larger machine to have the speed. Thanks in advance for any recommendations!..