g is 54Mbps
all other forms are variants of the "G" spec that use multiple channels to increase bandwidth, usually to 108Mbps
whatever spec you use, you must use the same technology with the cards
for example: super G router, needs a super G wireless card in order to work at 108Mbps
they also have "pre" N standard which is yet another variant
I say go with whicever brand you like (linksys, belkin, etc)