I bought my Powerback at the same time as I got the Powersleeks. The Powersleek is definitely superior for bounce control. Because I run sometimes (in addition to cardio kickboxing and other bouncy stuff), that's my top concern with a sports bra--it HAS to control bounce! And at 36C, I can't afford to let the girls loose once in a while.

Pros: It's OK for low- to mid-impact stuff, like regular step aerobics, elliptical, walking, or yoga. And it gives you enough separation that you look like a woman, not someone in an Elizabethan costume.

Cons: Just not enough support for the price. And the biggest PITA of all? Putting it on over my head! What good are back hooks if you have to hook them before you put the bra on? I never fail to catch the underwire somewhere on my head or neck and end up getting myself all tangled up in the stupid thing. If you have someone around to help you put your bra on before every workout, might not be an issue. For me, though, the Powerback is basically a bench warmer because it's such a PITA just to get it on. And it's even harder to take back OFF again if it's all sweaty and damp--you need the jaws of life to get you out of this thing.

Summary: If it's loose enough to get over your head, it's probably not tight enough to give adequate support for running. Well, that's *my* experience, anyway. Pass on this one, and get a bra you can hook normally.