Who said anything about track performance? As we saw with the G8 GT versus the SRT-8 Charger, the lack of power was essentially made up for with the extra cog in the gearbox and the slightest of weight advantages. Assuming that a similar system is applied again for the Camaro, I'm predicting a dead-heat between them. More gears helps the acceleration just a bit, not to mention the obvious increases in fuel economy.
Day-to-day driving and the occasional red light race is critical to the success of the Camaro against the Mustang and Challenger. Program a slushbox right or make the gears the proper width with the stick, they're going to make the pony car wars very interesting indeed.
Not quite the same scenario there, Brad (G8 GT v SRT-8).
Ratios on the G8's 6-speed box:
I = 4.03, II = 2.36, III = 1.53, IV = 1.15, V = 0.85, VI = 0.67,, Diff = 2.92
SRT-8/RT Charger:
1: 3.59 2: 2.19 3: 1.41 4: 1.00 5: 0.83 Diff: 3.06
In this case, it's a difference of gearing really. The G8 will get an early run (provided grip is there) but the Charger will reel it in thanks to the greater power.
Quarter times and traps:
Charger:
13.5 sec @ 106.3 mph
G8:
13.8 sec @ 102.8 mph
Of note, the G8 is 3 tenths quicker to 30mph than the Charger, but despite that, the Charger does indeed outrun it.
Now then... The Mustang V Camaro deal is a bit different at least on the stick side of things.
Ratios are nearly identical until 5th between the Mustang's 3650 and the average T56/TR6060, and I doubt there's going to be much difference in the final drive. Therefore, pull through the first few gears will be equal (just depends on what gets the better launch really) as well as overall performance. Well, highway fuel econ will go to the 'Maro.
Thing is, if the Mustang is going to keep a 5-speed, it won't be the 3650. The TKO might happen, but that said, it's not much cheaper than the T56s. So I can't see a Mustang with more power without a six-speed in the first place.
The (presumably) 3.5L, 265-270hp six will most likely soldier on with the TR3650 however.