Williams. He won so much in probably the most competitive and high-quality era snooker’s ever had. Plus winning his third world title 15 years after his previous one, and playing fantastically pretty much throughout.
I don’t think one extra Masters title makes up for the five ranking titles.
It’s a good question, though. Selby will almost certainly end his career more successful than Williams.
In terms of specific skills I’d say:
Potting - Williams
Breakbuilding - Selby
Safety - Selby
Tactics - Selby
Creativity - Williams
Temperament - Tied
Cueball control - Selby
But aside from breakbuilding, the things Williams is better at he’s far
better at, whereas Selby’s not significantly better than Williams in any one department. Plus you just feel
like Williams is the greater player.
Plus Ronnie mentioned him and not Selby as a great