If we're talking about cars that are currently available to buy new, I certainly wouldn't mind driving either of the SRT8's, but I'm kind of partial to the Chevy SS right now.
I daily drive a 2009 Pontiac G8 GT with the 6.0L V8, and I love it. It's awesome. I'm not a Chevy guy, but the G8/SS are made by Holden, in Australia. They've got it down. It's an awesome muscle "sedan", lol. I have a hard time calling a car with 4 doors a muscle car.
Anyway, the Chevy SS is, in essence, the upgraded version of the G8 GXP. Same 6.2L V8 as the GXP, but upgraded suspension, interior and a facelift. One of the car magazines did a comparison against the SRT8 Charger and ruled the SS the champ for a number of reasons.
The higher HP SRT8 was a little faster in the quarter mile, but the amazing handling, refinement, better build quality, and lower price of the SS won out in the end.