With ebo jager (old one before eheim took over) and fluval m series I had good experiences with. Stealth was bad for me when it either stop heating or another that sometimes turned on and sometimes not. Still haven't returned mines yet.
i own 3 hydor heaters and one eheim heater. I have no complaints with any of them. The numbers on the thermometers don't mean anything though. You really just have to adjust it manually in my opinion.
I highly recommend using a digital controller like this one. I have been using it for over a year and it is the best purchase I've made. It is perfectly accurate against both of my thermometers.
The only catch with using it is you have to do a bit of wiring, they do not have standard outlets on them. Basically if you can replace a light fixture, you can wire this. Also, make sure you get the 110V version if you are in the US.
Combine the controller with 1 or 2 cheap heaters and you are good to go.