First things first-
Hal- nice write up in Car Craft by the way (p. 27 for those who haven't seen it yet)
Now on to the debate. I agree with almost everything that has been said, especially Jamo and JWheaton's comments. I looked at SPF and ERA and both are great cars. For me, I just liked the body of the ERA better-(JW- I too thought Peter's real Cobra was an ERA, but I found out on my second trip there and didn't have to ask or get laughed at
). I never really noticed the "long nose" of the SPF . . . for me it was all about the shape of the rear deck/ rear fender/ rear tire relation. The ERA just looked a little wider- or a little fuller - than the SPF. SPF seemed a bit narrower and slightly higher in the butt than the ERA (not enough to qualify as "perky" though).
Also, I wanted to do some of the build myself. Somehow things feel "more mine" when they have some blood, sweat and (hopefully not too many) tears involved. (although at this point, I won't have much to do b/c I've just about ordered a complete roller).
Other than that, I think I don't have much more to add to what has been said already. Look at them, drive 'em both (if possible) and see which you like better. I really don't think you make a mistake either way.
Good luck.