Is there a noticable difference in the screen size/resolutions of the machine? I can see where the bigger screen could come in handy (doing mathematica and CAD work), but I need this laptop to come to class with me. As long as it fits in my bookbag, I don't care about portability. Does the 17" model look out of place in a classroom? I am missing my 20" iMac -- I have a 14" iBook G4 now.