I much prefer wild seas and medium fast. Vexing at least for strong players is never pure speed. In general very fast is very smooth and smooth and fast means strong players (strong putters) will make a bunch of putts. Only when a player is forced to play break outside the hole even on shortish (4-5) foot putts is he or she really vexed in my opinion.
I've played PV and the greens may have been a tad slow that day but I think they are as interesting and great a set of greens as I have seen. #2 green!?!? Amazing.
I'm not sure I'd call Merion "subtle" but in disproving my comments above I found it far more difficult to score on. Greens 3, 5, 9, 12, 15, 16, and 17 are subtle??? Anyway, excellent topic and give me wild, seas any day.