Lighter, mounts lower & more eye relief benefits the 6500. Optically the 6500 and 4200 are a wash best I can tell with my eyes. More mag is a plus...if you need it??? JMO but for a big game rifle 10x is sufficent for the majority of hunters (in field/real world speaking wise not internet blah....blah... . Price difference is moot in your case seeing you stated the 6500 was in your budget range. I say let your own eyes do the talking.

+2 on the talley mounts.

Good Luck