I play both sports. Tennis is much funner to play and a far superior workout. Golf is harder to play.
I'm not sure Federer is the greatest player ever. I think Borg might be. Sampras, in his prime, might be better than Feds. If Nadal didn't get injured, it's doubtful that Feds would've won the French for sure or Wimby.
Tiger is the greatest golfer ever. But, nobody has been able to step up and be a legit rival to him. Tiger has no Nadal, basically.
I think Jack had to beat better competition using shitter equipment than Tiger. I know players like Ernie Els, Sergio, Mickelson are great, but none of them have been able to make Tiger sweat....
I think it's harder to win a golf tourney than a tennis tourney....although it's very difficult to compare these sports.