If you already have an NSX, the SL might be a better car because the 996TT in many ways behaves like an NSX. The SL is a lot more luxury. But... the 996 will hold its value very well, much like an NSX, whereas the SL will continue to tank. Steveny is right, I would NOT, I mean no way in hell buy an MB of any type without a warranty. They are riddled with electrical problems and they are expensive to fix. Get a CPO car or one that has a CPO on it from an individual. FYI MB's extended warranty is only good if you buy the used car from MB, or buy from the original purchaser of the warranty. If the car goes to a used car dealer, that warranty is void. No matter what that dealer tells you. How does MB find out? I don't know... but they do.
Steveny, are you under a CPO/old starmark warranty?