Like I said above, given your intended use, a 300 to 500cc atv is all you really need. The large bore machines will cost you anywhere from one to two thousand dollars more. I've used my 300 Honda to pull out elk/deer and have even carried deer and an elk calf back to camp. Adult elk we usually carry on the jeep racks.
My Arctic Cat 500 (same engine in the Suzuki Vinson) has plenty of power and will lose traction before it bogs down. It has a hi/lo range sub transmission, and also comes with a manual or auto transmission (I have the manual). It will easily do 50+ which is way faster than I want to go on forest roads.
If you like to ride fast, want to beat your buddies back to camp, and have money to burn, than maybe you do need a big bore quad.
That's my $. 02