Consult your manual for recommended lubricats or call your local dealer. The main thing is to use the correct weight of oil, then buy whatever type you like. Don't be surprised if the book suggests Arctic Cat brand (Do your really think they refine and formulate their own?) No way. Just find out the weight and go with synthetic.
Hold on man, if you are running petroleum based oil now, then don't switch to synthetic yet. You aren't supposed to switch like that. If you want to switch, I think they sell half and half, or you can mix the oil yourself. But if you decide to do it, there has to be a transition. I am assuming that the longer and more gradual the transition the better it is.