They would be almost the same price with the 4000$ tax included.
I find the SRT8 interior to be a lot more upscale than the regular GC's actually, the seats and features are really nice on them, even the dash trim is a bit nicer compared to lower end models. I don't know how much they differ from the regular ones mechancially, but usually the performance line of Dodges are better quality.
With that said Mercedes isn't exactly known for reliability either, although it is admittedly a lot nicer inside.
The big thing is in this market I need to get a deal on the GLK, there is no way I am paying retail or settling for a crappy financing rate.