To be fair, git and mercurial are very similar. I wouldn’t recommend anyone to go with mercurial for a new project because of the network effects of git but I’ve used and been happy with both.
Many years ago I used svn at an old job. To be honest if I had to choose between mercurial and svn and death wasn't as option, I'd choose svn. Mercurial feels like the product of unsolicited help(which turned out to be the case when I read how it came about). And if you look at how it works underneath, it's practically the equivalent of trying to mass print books using Gutenberg's press in the 21st century.