The SL65 Black Series in stock form runs a mid 11 second 1/4 mile in the 125-126 mile per hour range. The GTR is lighter but not but all that much lighter with the SL65 Black Series coming in at the mid 4300 pound mark. It is also rear wheel drive with more horsepower and torque through the curve. It does not have the quick shifting dual clutch transmission of the GTR or the tight gearing down low. However, that does not explain how the GTR runs away at higher speeds where the V12's power should take over.
The only logical conclusion is that the GTR has more than we are being told. A disparity of 100 wheel horsepower at higher speeds where the tight gearing down low is not paying the same dividends simply should favor the SL65. Yet we see the GTR increase the gap up top. Video descriptions without dyno graphs or mod lists to back them are very difficult to take seriously with these types of results and we always encourage users to question what they see when the claimed numbers do not add up.
A stock SL65 AMG Black Series will dyno 560-570 wheel horsepower. With another 80 wheel it should be capable of at the very least matching the GTR trap speeds with the Alpha 6 package and realistically should pull it up top. Come to your own conclusion.