I use Eheim, Aqueon, and Fluval heaters and I've never had any problems with a single one. Except that ive never beeb able to figure out how to calibrate the Eheim's to their funky dial.
That being said ,I don't trust any of the heaters enough to run them without an external heater controller. Something like an Inkbird. Way to many horror stories of run away heaters on the forum to not have the insurance.