RE: open or firm??
I've got no experience with the Phenom shirt, but from what I've heard, it's pretty awesome.
Unless I've missed something, the open shirt is one helluva lot easier to get into, but you risk sacrificing weight on your lift for the convenience. The firm shirt will help you move a little more, but you'll need a couple of mates and a pound of talc to get you into it.
Hope that helps...