In my personal opinion the only mod to go for is CF when it comes to single player (Not open SP) I like the toughness of the mod as I always found vanilla waaaaay too easy!
However... When it comes to multiplayer I think it comes down to not only the mod features but also the community around it and sadly I can't say I like Disco... I tried it out a few months ago, went online and asked a few questions in open chat such as "Does this server run FLAC or FLHook" and other few things i couldn't find a satisfying answer to on their forum... And the results were players being rude both in open and private chats about me to "Go read the rules" and bla bla bla like that... So my personal experience tells me CF is the mod to go for when it comes to both SP and MP! The guys are strict here yes, but not rude when it comes to a new player asking questions to make sure he got everything right...