Tried both and it was a VERY close call...I still prefer the S4.
HOWEVER, if you're going for the turbine pro gold or copper, then it's no challenge to the S4...they just out flat destroy the S4 in pretty much every aspect.
You can get the Gold turbine pro at JandR for $80- than the amazon price. If you have the $ for them, I'd get them immediately.
EDIT: the only thing about the S4 is that they break down after a couple of months of use...the built and life quality of them isn't as impressive. I already had them break down twice...the second time just a few days ago...now I need to find my receipt to receive a new pair from Klipsch. 
Edited by bluntman - 7/19/10 at 3:03pm