Hey Ace,
Actually, the LSD provided MORE power to the wheel with the least traction thats called "Unloading the diff". for example when you are powering out of a corner and 1 of the tires lifts just enought o break traction it will spin more and unload the diff and keep the truck settled down so the other wheels can grab more traction instead of all wheels spinning and causing your truck to loop out. The Cross Pin Diffs Are More Durable and reliable cause they have a ridgid connection to the opposing spider gear so it keeps all four spider gears in the proper position inside the diff reducing the chance of failure.

The 40 series tires on a Matrix TR does not make much sense to me since they are taller and heavier, thus harder to build quick speed and create extra load on the drive train. But maybe those guys are changing the gearing to compensate for those negatives, but still not sure why they would go bigger and and strain the wheel bearings..The OEM sized TR wheels are lighter and smaller diameter, so would be better suitef for more snap and excelleration. Oh well what do I know..

I hope this helps