Marcus and Keith are both running them on double wishbone cars (s2000/RX8).
The word on the street is they like a bit more heat than Star Specs so don't expect your fastest run on the first run. Since the 328 is on the heavy side AND has struts, you should be able to get some heat in the fronts pretty quickly. But also that they drop off like a cliff if they get TOO hot (the camber gaining cars mentioned above probably won't have as much problem if at all with this) whereas the SS is more of a gradual trend towards greasiness so in NC summer events you might have to deal with some spraying with a codriven car.
Rain performance goes handily to the SS.
SS has stiffer sidewalls.
However at a $140/set difference it's probably worth giving a shot to see how they like a strut based car.
Are your wheels 16x7.5?
EDIT:
Keith and Chris run RS3s on the SMF cars they run. A good bit lighter than the 328 but still struts in the front. Looking at their times, it doesn't seem like the RS3s are holding them back

.