in straight line performance you are looking at the GT-R at 11.9@120mph, the Boss 302 is at 12.3@115mph so obviously it's faster there. look at the gtr weight, 3885 55/45 distribution, the boss is 3631 (having trouble finding weight distribution info, i saw a vid that said it was ideal though) tight suspension, sticky tires, good brakes, from the facotry it was built for that kind of track.
http://www.motortrend.com/roadtests/coupes/1102_2012_ford_mustang_boss_302/specs.html
"The Boss 302 and Boss 302 Laguna Seca are absolutely amazing machines and we tip our hats to Ford for not simply wimping out with a sticker and wing package. So who's next? That's a good question, because while the new Camaro ZL1 has dramatically improved suspension and 550 horsepower, we don't think it stands a chance against this Boss on a race track. But we look forward to finding out"
THe leguna seca edition has the rear seat removed

that model hasn't been tested by journalists yet.
That track is kind of interesting.. and the results of the gtr beating the zr1 always made me wonder about that nurburgring run.. i know that it has been debated to death, on paper there is no reason the GTR should be anywhere near as fast as it ran. a 3885lbs 480hp car shouldn't be beating a 3300 638hp car.. and on race tracks driven by pro drivers the ZR1 has been beating the GTR.
edit: just saw that the list has been updated, more people have taken the GTR to the track it seems.... same driver in the zr1 and the gtr eqauted to about equal times.. interesting.
i'd like to have a GTR as well, but for 41,000 thats some good bang for your buck.