I cant vouch for the SS as i've never driven or ever even sat in one. but I can say that I love how the Z drives head and shoulders above my dads challenger.
(which I know is not a camaro. but it is a big, heavy, car with more horse power.) it felt like I was driving a boat.
I hear the camaro z28 is coming out next year. I'd wait and test drive both before I decided. (i'd also recommend asking this same question on a camaro forum.)