Saturn Redline Curbweight is 2,930 lbs
Chevy Cobalt SS Curbweight is 2,806 lbs
The Cobalt SS is lighter and I belive they even changed the gearing also on the Cobalt SS to use more of it's powerband, On the RL the you hit the Rev Limitor and you are still gaining power. I have heard that if the RL was able to rev an extra 500 - 700 RPM's that it will reach it's full potention and when you shift you will be able to keep the RPM's above 4,000 where you make real good power. I am not positive and don't quote me if I remember right I heard a someone on the Cobalt Design team say something along the lines that there were canges made to the Cobalt SS to reach more of it's potential power.
Also on the J-Body Orginization there was a good thread/debate on the 2 cars. I suggest reading the thread and make your own opinion about what is faster.
http://www.j-body.org/forums/read.php?f=6&i=68188&t=68188&start=0