Go with whatever you think looks better. I think New Edges look better in general, but then again, it is a Cobra
vs. a GT we're talking about here. Toss up in my opinion.
Also, the difference in performance is actually quite small between the two. Yes, the Cobra makes more peak power, and yes it can rev to 7000 rpm, but the 2-valve PI has a broader powerband that makes significantly more torque lower in the rpm range. Stock for stock, it's pretty much a driver's race with a tiny, tiny edge to the Cobra. And comparing modded setups, the Cobra doesn't really
start to set itself apart until you get well on up in the power levels, like 500+, when the 2-valve heads start to choke up a bit.
Surprising, there's probably more aftermarket for the 2-valves than there is for B-headed 4-valves.
Depending on how much more money you're looking to spend, I still think a 03/04 Mach 1 is one of the best bargains out there right now. I see them for under $10k all the time in pretty good condition. They're significantly faster than a B-head Cobra or 2-valve and respond well to mods, there's plenty of aftermarket, and I personally think that they're easily the best looking SN95s ever made.