Atleast at Wimbledon it feels like theres more exciting matchups.
Who really cares about a 55th ranked Spanish guy playing a 77th ranked Argentine?
It'll probably go 3 boring sets with a ton of stupid, long baseline rallies and really theres no telling who's going to win.
Its not only boring gambling wise but also aesthetically
Wimbledon is beyond comparison with anything else, it's by far the most exciting tournament in the world...but clay court mugfests can also be mildly entertaining, especially those SA ones... I'd say that maybe best of five is more suited to grass/hc where the action is faster than it is on clay.
With regards to upsets on slams/masters v upsets on challengers/lowly ATP tournaments I'd say there are upsets and upsets. Rosol beating Nadal was a major upset but also a great tennis moment...also Tipsarevic beating Monaco today was an upset but a deserved one...however, an upset as a result of fixing a match or of showing up just for the appearance fee is not a good upset...you have to go deep into a non slam/master week to find a day where those factors don't play a negative part.