in my experience quad specs are irrelevant in the real world as they don't translate into actual ability, the 420 and 450 are equally sized and equally capable bikes and both 420cc. 500/520 is a much bigger and more capable bike, though not any faster. My 500 has had more than the actual capacity on it most times it has been used and it is standing up to it much better than my last Yamaha (550) which was supposedly bigger and more capable.
I know the Specs are only a guide, but why list lower capacities. Makes me think the manufacturers aren’t as confident in their product.
towing weights are normally governed by the braking capacity, and the Yamaha’s rear immersed brake is excellent and virtually maintenance free.
Also when comparing price, the basic 420 has no irs.
Ive had probably 10 Honda’s, starting with three wheelers.
Got the Yamaha 10 years ago, and kept it.
Never kept a Honda as long as they always started to give bother.
Shift fork broken on 450es, then it dropped a valve seat, and bent the con rod. Speaking to breakers for parts, they had a few bikes with the same fault.
I was warned away from the 420 Honda then, but I hear they are better now.
Would be hard to look past the Yamaha in my experience.