He's right that the white Macbook's (at least first generation, don't know about the recent ones) use shared memory for the graphics card. But it doesn't affect the performance especially with 2gig of ram. And it doesn't take 'a lot' of memory, mere 64mb as default. We are not living in the 90s anymore, todays computers have much more ram than 256mb!
Naaaaaaah! Macbook is a modern computer and can deal with Os X graphical interface! It may take more memory than Windows XP gui (definitely not more than Vista) but it can deal with it easily. And with default 2gb of ram there's absolutely no slowing down because of the interface. And btw. you can turn off most of the animations etc in Os X if you are concerned about the performance loss because of the slick interface (I think the so called 'performance loss' is negligible anyway). Did your boyfriend make music on Os X? I don't think anybody who knows this platform can seriously claim that he can't make music on Mac because the interface is taking so much memory and slowing everything down. It's the first time I hear about it 
And just for the kicks, for the first year I had only 1gig of ram on my Macbook. I still made awesome music and played live in the hippest of clubs so there you go!!!
If think you could be surprised how capable these white Maccies are...
But in the end it boils down to personal preference. I'm not a Mac zealot although I seem to be one, Macs are not without problems either. Still, don't go with the cheapest pc laptop brand!