I plow with a 1994 Polaris Sportsman 400 4x4 with a 50 inch plow. It would work great for your purpose. I plow my long driveway and it pushes it fine every time.

 

Its more about chassis size than motor size. A 450 Grizzly and 420 Rancher has a smaller mid size chassis than a 400 Arctic Cat or 450 KQ which have full size ATV chassis's/frames even though there motor sizes are the same.

The newer 450 Sportsman is a much smaller ATV than the older 450 Sportsmans.

 

the key is traction. use weight as suggested if tires slip, but just about any 4x4 will plow. my rubicon is slick because of the smooth hydrostatic tranny that is built for work. i also recommend a winch to raise / lower the plow blade. in your case, i would go for reliability and research models that way. good luck!