I've been in a 12 team dynasty league since 2012. In the 13 years our league has been active we still have 11 of the 12 original members. The guy that isn't in it anymore was kicked out for too many shenanigans/shady trade tendencies over the years until he royally pissed off our commissioner (who is usually a pretty mild mannered guy) and was booted.
There's no league as good as a dynasty league, all the guys in ours love it. Super active with trades.
I still don't mind redraft leagues but they aren't quite as fun usually, depends on the group that are members of the league, ultimately that's what makes a fun league regardless of format.