I'm not sure where you got your numbers, but Chevrolet's website says the 2.7 has:
310 hp [231 kW] @ 5600 rpm
348 lb-ft of torque [471 Nm] @ 1500 rpm
And GMC's website says the 6.2 has:
420 hp [313 kW] @ 5600 rpm
460 lb-ft of torque [624 Nm] @ 4100 rpm
That's a difference of 110 hp and 112 tq, both in the 6.2's favor.
Regardless, I'd like to see what you thought of the 8 speed vs the 10 speed transmission. I've heard the 8 speed is garbage, but have no first hand experience.