I have the Daystar and my son has the classic.

I bought the Daystar because I'm busty and the Daystar has straps that are designed for women. The sternum strap is a little higher and the straps are curvier. When I have worn my son's classic (I think that's what it's called--70 oz, just regular stuff on it--it might be an old model), the sternum strap and shoulder straps kind of squeezed me inaccurately. But the Daystar doesn't do that.

If you're built like a boy, it doesn't matter that much...but I'm a DD.

I bought it for our trip to Santa Fe, so I haven't used it much, but I've used his a few times. I think filling it with icy water would take care of the sweaty back problem.

(Advice on MTBing in Santa Fe welcome! I'll be there on Labor Day Weekend.)

Karen