i've got both, and ultimately both clubs are the same... both come with free training sessions when you sign-up, but the training sessions they give you are pretty lame. it pretty much just depends on the particular facility you go to. i've been to some really nice bally's and some really ghetto ones, and the same goes for 24. the 24 "sport" clubs are often a bit nicer with newer machines and more helpful staff, but there's an extra fee to be able to use the "sport" clubs...

i'd choose which ever club is closer to you, 'cause the more convenient it is, the more likely it is that you'll go.