the approximate power to weight ratios are (higher # is better)
SS: 4500/400 .08888888
4.4i: 4900/315 .0642
4.8: 5019/355 .0707
0-60:
SS: 5.7
4.4i: 6.8
4.8: 5.9
BUT, the kicker is $$$$:
SS: ~ $37,000 loaded
base 4.4i: ~ $54,000 no options
base 4.8: ~ $71,000 no options
The intangibles/variables are too numerous to list, but based on the #'s above, the SS wins on performance/price.
And before everyone starts flaming me, I own both a 4.4i and a Corvette Z06, so to say I'm biased one way or the other isn't a valid argument. And while the argument can be made that an X5 is more reliable, ask someone who has replaced all 4 window regulators, their cv boots, and front control arms on their X how reliable their X is. Trailblazers have their problems too, like brake light assemblies blowing and HVAC fans needing to be replaced, so each has their foibles. Obviously the BMW has more snob factor (it's ok to admit it, we all know it's true...
), but it's 2x the price of a TB SS ....
anyway... dems da facts.