Agreed.
I'm running a Mach1 8.8 with 3.55's and it did have some improvement over the GT 3.27's 8.8 that I used to have, so yeah, I think the 3.55 does offer a little benefit that would tip the scale in a direct comparo.
Gotta remember though that the IRS you guys have is 85-87lbs heavier than a straight 8.8 axle.
Don't freak out with the above photo. There are no control arms and (upper & lower), no shocks, no calipers/brackets, rotors, etc on the straight 8.8 :bored:
Oh I know we have some extra junk in the trunk but I love my IRS, it rides amazing compared to the straight 8.8 for around town and in my experiences makes the car more fun in the twisties.