It's difficult to compare leagues, since new leagues have more to build on.
W:ACL was made during ranks and therefore didn't need a singles league.
cl2k started when the worms community was still growing and therefore could function well with a 40 games limit
WL (should've been included in the poll) was the first to implement official tournaments (at least, I think cl2k didn't host any tourneys themselves)
FB innovated in that it was the first league to have ratings implemented, eliminating the need for a game limit. It was also the first league to make use of replays in the system. They were also kind enough to keep one saturday free of tourneys for RRkit even though they wanted weekly tourneys

TUS took the FB concept (or MI thought of the concept himself without that example, I don't really know!) and implemented challenges and cups into the system.
All in their own way added new elements to the game and all were/are successful, but the later ones have the benefit of not having to reinvent the wheel. If you're looking at what the features of the league are, TUS wins out. If you're looking at what new things the leagues have accomplished, they have equal success imo