As far as I'm awear the lsd diffs are the same.
As with most things to do with gq to gu.
Small clutch?? Well I guess that depends on the engine. Pretty sure the 4.2 engines are pretty similar across the 2 models.

The main difference is the front diff.
The gu has a 50mm wider track over the gq. But it's also much beefier in the cv knuckles and the cv's themselves.
There was one diff which was different to the rest, and from memory that was the 4.8 petrol gu I think. Was a larger one. But unsure about strength.

As for the ratios. Well they vary depending on engine, transmission and year.

Yes the gu is heavier, but that's no big deal. Makes a nicer ride.