Basic rundown of how I feel about the various CM Storm keyboards:
Rapid is not one you mention but there's a reason it's one of the most popular keyboards on this sub. It's reliable, portable, and it does the job for most keyboard enthusiasts (at a great price, too). If you're ok with tenkeyless, QFR is for you.
XT is what I consider to be the quintessential full keyboard: not flashy, but it does everything any hardcore typist or gamer needs. I would absolutely recommend it if you need a full keyboard but you don't require backlit or any non-functional additional features.
Pro is a slightly fancier looking, partially backlit XT. Pretty meh, imo.
TK uses the numpad for arrow keys, and that could get annoying really fast, but it has a smaller profile if that's important to you.
Ultimate is the full-on flashy look-at-me-I'm-a-gamer keyboard of any pc gamer's wet dreams. If that's what you want, that's what you'll get, and with all the CM Storm reliability.
tl;dr QFR is a great TKL, XT is powerful and simple, Ultimate has balla swag, and the others aren't that great imo.