How do the various SSH daemons that run on Windows compare in terms of security? Vulnerabilities found, reviews by respected reviewers, source code availability, etc.
I only need access to a cmd shell.
(updated to be less subjective)
Well, we're certainly not in a place to judge that. It's hard to do so for most software in an objective sense, and it's rather useless in a subjective one.
With that said, OpenSSH is widely used and widely trusted on Unix systems. Cygwin allows that code to run on Windows. I'd go with the Cygwin + OpenSSH method as you don't have to trust a more obscure vendor to get the implementation of SSH right.