Tire size for Polaris 570 eps

Which tire size will give me the most ground clearance?

You can go real big but I wouldn't go too big. Bigger tires cause drivetrain issues. Also cuts horsepower bad

If it were me, I would go 26" and invest in a nice set of aluminum skids.  Skids will make you go better than those huge tires because you can hit stuff a little faster without worry of doing any damage.  If you go from 25s to 27s you will only gain 1" of ground clearance and kill your power bad, as well as put more stress on your axles and belt.  You could go with a lift, but that will put more stress on axles, and make it ride rougher.  Most mods are a trade-off.  In most cases, what makes you go better makes you slower and less reliable.  You will be easier on your machine by hitting stuff hard than you will be by running huge tires and bad cv joint angles of a lift kit.  It all depends on your riding style and the trails you spend most of your time on.  If you are a slow moving rider that hits every mudhole you come to, then a lift, big tires, and a clutch kit are for you.  

Tell us about your riding.  Do you hit all the mud?  Do you like to ride at a faster pace? etc.  I would like to have the money I spent over the years on stuff I thought I needed, that way I could spend it on the stuff I know I want now.

Buddy of mine has 26s on his 570. Looks a lot better than the stockers it came with. Good size for that machine IMO.

WELL SAID  HUMP

26/9/12's on all 4 wheels. Best option for giving you clearance and preserving Horsepower.