Without a doubt the caincase and oil tank improvements from a belt drive are much better! Definitely one of the biggest benefits.I put a TKI belt drive on my 2016 AXYS that came factory with the Polaris Quickdrive system. The TKI was heavier because of the tensioner. There were noticeable performance gains because of gearing and because it rolled so much easier than the stock system that had to be run "banjo tight". The rotating mass of the chain drives is huge and more noticeable even when the total weight including gears is not much different. The Cat oil tank is also not the best design when it comes to access to the chain case for maintenance.
You are right about the chaincase guard. FWIW a good portion of my Cat customers buy the belt drive kit because they broke the chaincase.if its even quicker response than the quick drive, thats sayin something for sure. the maintenance thing with the chain case is no big deal imo. basically maintenance free. just change the oil often, which is easy.
I think you can add another pound of weight savings to the belt drive since you probably won't worry about a chain case guard. something that's on my list still. so not too bad bang for your buck really, nice mod!