worst is git by far. i'm used to it now but when I was learning, "what the fuck did `git reset --hard` do? where is --soft? Is there a no-flag version? What the fuck did I leave mercurial for. God damn I miss svn." I still kind of miss Mercurial and TortoiseHG.
Mercurial was much better IMO but people argued about performance, because, you know, the CPU is the bottleneck when I merge code. How much time has been wasted navigating Stack Overflow?