well i got some good news for you i happen to have both atvs here i got the two on the left my brother the one on the right here is what ive seen and expierienced the 500 and 420 are identical the problem with the 420 its to light to pull what a 500 can its gona spinout befor you dont have the power to pull it the 500 you will get that same thing they both will pull way over there tow/ pulling limits but the honda 420 is lighter keep this in mind the foremans they are heavy the es i dont like it its not as controled theres been problems with it i like my on the fly mannule 420 it takes off faster its able to get what i need done how ever the 500s that have 25s do have more gound clearence BUT they lack adjustable shocks witch the 420 has you can make the 420 taller or lower i put 25s on my 420 and put the shocks up as high as they would go and it out hights a foreman by roughly 3 cm but if you lower it tis about 10 cm lower and 4 cm wider in stance this is a pluss when trial riding you have to think about whos riding the trail a 2wd or 4wd if its a 2wd they generaly dont tear up like a 4wd in the mud they get stuck pick up there atv and take off a 4x4 will tear up a nice rut and then you have to try to get through its just bad stuff its all on prefrance my friend if you have any quesitons let me know
my 420 had 25 dirt devils and extream 3000 pound winch
500s are stock

 

I have been trying to make this decision and have bought an 07 rancher. I would say you need to get out and ride them. I was coming from a Kawasaki Bayou 300 and the Foreman just felt to HUGE to me. Love the FI of the Rancher. And My rancher 420 is not IRS. It has a solid rear axle.