Most of you have probably forgotten this by now but early on when superchargers were just being developed for the E9X M3 people would claim kits using the self-lubricated Si-trim were superior to competitors kits offering the T-Trim option. The BimmerBoost position was that the T-Trim was the better blower as it can move more air as it is spun faster and also that it has more room to be overspun. Essentially, it is capable of more power.
The overlay below illustrates this well on the same S85 5.0 liter V10 engine which is capable of maxing either blower. The T-Trim simply flows more air up top:
These are both good bowers and each has their own advantages. Some people like that a blower is self-lubricated and others prefer that they change the oil in the blower frequently. When it comes to performance the best blower is the one for the VE (volumetric efficiency) of your motor but in this case the T-Trim will always make more power on the S85 V10 than the Vortech Si.
Here is the Si Gintani Stage II graph alone:
Congratulations to Gintani for raising the bar again and catering to customers with multiple options and not a 'one size fits all' approach. There is a rumor with some traction that BimmerBoost will vouch for that Gintani will try to fit something even larger than either of these blowers in the near future.