On a road course, especially tight ones, I'm sure an elise could blow a viper away. On autocross definite nod to the elise, drag race, forget it, viper by a mile.
Even tight road courses I give the Viper the nod (with equal drivers). The power to weight ratio advantage is just too great. Not to mention the Viper is no slouch in the corners pulling over 1 g, and goes extremely fast through the slalom. Although, the Viper is much more difficult to drive fast, and takes an experienced driver too extract the venom.
When I drove an Elise 111S, I was driving at the razors edge (9/10s) in 20 minutes. The feedback this car gives is amazing. Kinda like a go-cart. Just no balls... I have had my Viper GTS for nearly 3 years, and felt more confidence in the twisties after 20 mintues of driving in the Elise (than the Viper). Kumho R compound tires did help with feedback in the Viper, but still no comparison to the Elise. IMO, steering feedback is the Viper's biggest flaw. Don't get me wrong, I'm crazy about the Viper, as no car is perfect.
IMO, the Elise would be a real contender with 300 HP and more torque. Maybe the aftermarket will come up with something good, but I haven't seen it yet...