The 3.31 will get you better low end acceleration with slightly compromised fuel mileage. The 2.73 has good acceleration (not as good as the 3.31) but it's main focus is fuel consumption. For a fun car, the 3.31 is the only option.
2011 MCA V6 Coupe, Ebony/Charcoal, 6 SP M/T, 3.31 Rear End, Security Package, HID Headlights.
Tint, GT500 Rear Diffuser, 401a Knob and Boot, Roush Axle-Back Exhaust, Roush Extreme Lowering Springs
Ordered: 3/20/10 | Pulled: 4/8/10 | Built: 4/19/10 | ETA #1: 5/6/10 | ETA #2: 7/15/10 | Delivered: 7/24/10