09R/T_Semper: I also am concerned about fuel economy, and I came to the same decision as you - an R/T with MDS. It's not ideal, but very close. I wish the Hemi engines had aluminum blocks, though. The V6 version is around 200lbs lighter!
I considered the V6, but I decided against it for a few reasons (besides just wanting the R/T and Hemi badges and all that they stand for). First of all, the V6 is only rated at 2mpg better. Along with that, I have read that the engineers don't think the MDS shows its full potential in EPA testing - which means that in the real world the fuel economy of the V8 might be better than what it is rated at. (This concerns the new engine, the one rated at 370hp. Apparently the MDS has been tuned to operate even more frequently). Finally, the kicker - the V6 only has a four speed automatic. If it had a 5 speed I would be torn, but for now the decision is easy. Under light driving, the R/T will have 4 cylinders controlled by a 5 speed transmission, as opposed to the SE's full-time 6 cylinders controlled by 4 speeds. Thinking of it that way, the V8 is almost better. Certainly the better all-arounder.
However I hear they are working on a new generation of V6 called the Phoenix. It should be even lighter, more powerful, and more fuel efficient... and if it's paired with a 5 speed auto (or even a six speed auto!), that would be ideal for me. For now I'll "make do" with my Hemi.
