Goodhart, read this article if you haven't already. I tried to include all the info about the difference between the calipers for different years and models
http://www.dsmtuners.com/forums/arti...brakes-1g.html
My only comment about the 4 piston calipers is that the 4 piston calipers will be wider on the outside, so there's more potential for wheel/spoke interference. Non-issue as long as your get the right offset wheels, but just something to keep in mind when going 4 piston. For Evo components, I don't own an Evo so I don't know but are their caliper/rotors/pads available to the point that you can just drive to your local Napa/Autozone and they'll have them all sitting on the shelf? That was a huge plus for me for the Cobra's. I'm sure the Evo's stop better, but the Cobra's had plenty of stopping power for me when I was trapping high 130's. For me it was the balance of performance, price, options, and immediate availability that led to my decision to use them.
And Steve I really liked how they look, I think they look nicer than VR-4 brakes. But that's all a matter of individual perspective I suppose