This is true. Very close in performance but the 4.6 GT from 2010 is faster than most stock V6. Well faster than the 2011 V6s with 2.73 gears for sure. I own a 2011 V6 and I know the GT is faster.
With the previous V6s I would not bother to add turbos or superchargers of any such mods. In most cases you had to pay a lot more to get to the performance level on the GT. Even if you could make the V6 more powerful than a stock GTyou also had to mod brakes, shocks, rear end to an 8.8, wheels and tires to match the overall performance of the GT. It could be done but for more work and more money.
These days you get a better starting platform for the V6. Now the V8 will always have the upper hand but it is nice to see a modded V6 get out and fight it's own battles with other six cylinders like the Nissan 370 and the turbocharged BMW 335i.
The V6 mustang with the "Performance Package" actually handle better than the 5.0 GT with the "Brembo Package" now that is amazing.
Yes, the 2010 GT is a few tenths quicker and a few mph faster 1/4 mile.