I think other links are welcome, this topic becomes a good reference on the topic... :-)
This kind of software is critical, so good functionality and reliability is important. Something often overlooked is to check the result: how easy is it to get some archived file, without unarchiving gigabytes of data?
Indeed, Cobian can run as service, at given intervals, that's nice, but of course, one can use the standard task scheduler to program backups, as long as the software has command line options.
[Cobian] have a couple of advantages over Abakt like built-in scheduling and the ability to run completely hidden.