In terms of pure golf, it could be argued that pros would want to win the US Open or the British Open the most, after all, they are truly open, has just about the toughest field (maybe the TPC is the toughest, IIRC), and it says you are the best golfer in the world at the moment. And they are almost always played on historic iconic courses.
OTOH, gun to their head, I bet 90% of pros would choose to win the Masters over any other, for one, I think the off course endorsement revenue would be the max for the Masters, and then if for no other reason that you get invited back every year of your life, to attend the Champions dinner, par 3, and play in the tournament until you are 65 or so.
As one pro put it in an interview I read a while back, "who in their right mind would even
WANT to play a US Open course every year the rest of their life?"