1. daemontools and runit are practically identical. I do prefer runit somewhat, as svlogd has a few more features than multilog (syslog forwarding, more timestamp options), and sv has a few more options than svc (it can issue more signals to the supervised process).
2. Among the criteria I look for in a process manager are: (1) the ability to issue any signal to a process (not just the limited set of TERM and HUP), and (2) the ability to run some kind of test as a predicate for restarting or reloading a service. The latter is especially useful to help avoid automating yourself into an outage. As far as I'm aware, none of the above process supervisors can do that, so I tend to eschew them in favor of initscripts and prefer server implementations that are reliable enough not to need supervision.