This might be a downer for you to hear but...
Honestly, I ran a belt drive on my t3 and the only thing I noticed was that I spent $800 plus buying an extra belt( total around $920). No performance gain - no faster spool up, didn't require any clutching changes. Two things I did notice, I spend nearly 1Kand it sounded a little different. I was really hopeful and wanting to believe the 'less rotating mass' and less weight. We installed 3 of these that year and none of us have spent the money to put one back on our new sleds. Now, if my sled came with a belt drive I would keep it but I did not and do not see any reason to spend the money for a belt drive. I have a turbo G4 now and do not miss the belt drive
This is definitely not our experience but we ride mostly Polaris.. They roll so much easier. Our shop sled is a Doo and I believe for some reason it is a bit less noticeable because the sled is already so much heavier.