Several people have already said it, being able to pivot on the pegs allows you to position your weight better on the quad. Any radical riding, steep hills or technical off camber stuff, the pegs are better. For cruising and relaxing rides the floorboards are nice for keeping stuff off your feet. I have both and I've had my Polaris SP335 in some steep situations, where the raised foot peg area held my foot ok, but I would have been more comfortable being about to rotate around on a peg.

 

In response to the guy who said that he doesn't like the way your foot has to be flat with floor boards. With pegs, your supposed to keep your foot flat too, because it you point your toe down, it could catch on something and break your ankle. Believe me, it happens, i didn't break my ankle, but I hurt it pretty bad