If you have a 54G built in wi-fi card on either an Apple or PC you should get very similar speeds. The Apple airport wi-fi router can be used with PC or Mac and I think D-link, Lynksys, Netgear, etc should work with either type also.

You can get 108mps wi-fi routers but the highest you can normally get with an internal minipci wi-fi card is 54mps (G backwards compatible to b). Just make sure you get an Intel 2200b/g or equivalent and not the b only.