The second generation is MUCH more powerful! 393 hp vs 325 hp and the torque comes in at a lower RPM on the second generation.
2005 Hummer H2 SUT Compare Car
0-60 mph 9.5 | Quarter mile 17.1
2008 Hummer H2 SUT Compare Car
0-60 mph 7.9 | Quarter mile 15.8
https://www.youtube.com/watch?v=11wBxzF4tQg
150 km/hr video = 93 mph