while i think the blackbook is the prettiest of the three, if you're even an occassional gamer, you should forget about the macbook line. an integrated video card just wont cut it for 3D gaming.
i actually was a lot like you when i was shopping for a laptop. an industrial engineering student who also gamed here and there. i ended up going with the C2D 15" MBP 2.33ghz. Although you probably wont see much of a performance difference processor-wise, 2gb of RAM is the sweet spot these days, and the extra video ram was a positive point as well. therefore, id suggest the higher end 15".