It has to do with the design of the head.  I run 93 in my 500 and haven't had a problem.  I have a custom dome matched to the piston and it's been ported.  Always run the lowest octane required for your quad, otherwise you are pissing away money and losing power due to less energy in the fuel.

High octane fuel has more resistance to detonation.  If you put high octane fuel in your engine and it makes more power it was because your engine was not jetted properly or was having a detonation problem.  High octane fuel DOES NOT necessarily have more energy in it.  Gasoline's energy content should be in the range of 17,000 to 20,000 BTU per pound, anything outside of this range cannot be called gasloline.

Your engine build specifications is what makes an engine produce more power not the fuel that is run.  The majority of the high performance engine builds require higher octane fuel to protect the engine from detonation.