First observation. I dislike the way the phrase "best golfer" is most often used -- which is to identify the most skilful player. For me, the best golfer has little to do with skill, and most everything to do with how one plays the game, in the human sense.
Second observation. I like to think of golf as a variety of different games. On day one, A wins an 18 hole game over B at medal play. On day two, B wins an 18 hole match play event over A. Then, A wins 8 out of 15 36-hole medal play events over B. B wins 9 out of 15 match play 36-hole events against A. Who's the more skilled golfer, between A and B? Tiger wins X majors and Y total world wide events. Jack wins Z majors and XX total world wide events. Who's the more skilled golfer?
Third observation. The question is not answerable without a pre-agreed standard, which ain't gonna happen, but as we are doing here, it sure is fun to discuss.
Fourth observation. My understanding is that as best the historians have been able to determine, golf competitions began as match play events, either as knockouts, one vs. one, or scorecard matches among the field. Medal play came later. Does that make match play the premier measure of golfers' skills?
Fifth observation. In my personal experience, medal play is a more difficult game than match play, primarily because the strategic considerations are more nuanced. In match play, a decision or ball strike can cost you a hole. In medal play, a decision or ball strike can cost you (via difference), any number of strokes, with X holes remaining to make up Y strokes. Still, I am not willing to concede that the the medal play winner is necessarily a more skilled golfer than the match play winner. For me, they're different games.