As far as power performance, they are the same. The GS may be a tad bit quicker because it has a better set of tires from the factory. I also believe the GS has a beefier suspension (anti sway bar), RS does not have one I believe. It'll most come down to who is driving each car though.

I also agree with the others. There is alot of information on the internet on these cars. Almost any basic and even moderate/technical question can be answered by searching the net. You'll probably yield much better results at http://forums.2gnt.com/dcboard.php (forum for 2nd gen non-turbo eclipse/talon owners).

Cheers.