First of all, it’s Mac, not MAC. Unless you’re talking about cosmetics or you’re really happy to be discussing the platform, it shouldn’t be entirely capitalized.
Secondly, how open is he to learning another OS? Is he fixed in his Windowsly ways, or can he start fresh and not get frustrated by the unfamiliar nuances of the Mac OS? I ask because recently another poster was given an iMac as a present, and, well, she hated it and had it returned. If you’re sure your RM is open to a Mac, then go for it. But there’s a bit of hesitation, then why try to convert him?
You should take a look at what you need the computer for, and then do some homework: can a Mac do what you need it to do? Can the PC do it better? Investigate what software titles you plan to use; is there a Mac version? What are the differences between the Mac and PC versions? If the Mac can do it better, how well does it fit with you? Can you both be dual-platform people, and happily? Is it within your price range?
I’m a Mac user, and I like seeing people try the Mac. But I prefer that they know what they’re getting into, lest they have a negative experience and blame it all on the platform. And no offense, but it seems to me the only reason you’re considering a Mac is because it’s different, and that’s silly, IMO.
Third, Mac gaming used to suck ass. There were maybe three companies that did Mac games. In the last few years it’s gotten better. Mac magazines actually have a games section now; their mentions of games were kept as sidebars or in reviews only. A good portion of PC game titles are either available for the Mac or in development. And in turn, Mac hardware is improving to meet the demands of game software.
Still, there are drawbacks to Mac gaming. Titles are seldom released for both platforms concurrently. For example, Max Payne for the PC has been on shelves for a while; the Mac version is either fresh out or won’t be out for two or three months more. Second, like with other types of software, the Mac adaptations sometimes lack features, have a different design, or are sloppily done. Third, there is limited support for games in OS X. Patches that allow gameplay on OS X are iffy, at best. Lastly, it takes a fairly new computer to run the most popular and recent games. My iMac is under two years old, and I estimate it can’t run 50% of the games out there, and I’m betting it can’t run any game that’s been released in the last 6 months. You’ll have to get a fairly new machine, and that means spending more than you would for a PC. And money seems to be one of the primary reasons why users choose PCs over Macs.