What points are even being argued any more?
I think it's probably safe to say a ZL1 and a 2012 GT500 would be drivers race in the 1/4 mile, I say look no farther than power-to-weight ratio for that. Of course there is more to it than that, but still they are almost identical in that regard.
Similarly, I think it is also safe to say that if 2010-2012 GT500s have hit 11s bone stock, a ZL1 will eventually do the same.
l think it would be a crying shame if the 650hp GT500 can't hit high 11s in the magazine tests, based solely on what we know now. Besides drag radials are just too cheap and easy to remedy any limitations of the stock street tires if for some reason the 2013 GT500 is still stuck in the low 12s.
Personally, I only remain skeptical on the 2013 GT500s road course prowess. Note I said "skeptical" not "in denial"

I just want to see/read reviews before I make a judgement.
On another note, I'm pretty sure the ZL1 was tested against a Boss 302 LS, because they are both marketed as the more track oriented models of their respective brands. Not because anyone was afraid of testing a ZL1 vs. a 2012 GT500 on a road course. Besides I think for the time being, the Mustang Boss 302 LS is the sweetheart of the media, at least until the 2013 GT500 is out on the roads. I can't tell you how many times I've read that the Boss 302 is the best mustang ever.
I personally can't wait for the $h!tstorm that will be this forum when the '13 GT500 vs. the ZL1 review finally hits the public. I pretty sure no matter who wins, it will be a circus of excuses and explanations