As surprising as it may sound, I like to use a (quality) heater on its own but with supervision from my tank controller:
I get SMS and email alerts of gross temperature excursions as well as plug the heater into a controlled outlet that
will be killed if the heater goes "bananas".
This scheme is not 100% perfect as the outlet *could be* switched off by a goofy controller off but overall,
I prefer the "layered" security of this scheme rather than put all my trust in either the heater or the controller.
What can I say, I work in electronics (hence the username) and don't trust the stuff 100%...