I tried some of the Titanium heaters, from Won bros, etc. The couple I bought, stopped heating and working after a while. The heater didn't kick on.
What I have usually used, and I think are the best - are the heaters from Rena Cal Excel. They have a red light that you can see go on and off through the glass tube. I like that because if you know the water is warm or the temp is warm and you see the heat clicking on, its a signal to check it out. The little red light is also a way to know that the heater is working. The titanium heaters you can't see that well. Yes, some of the models have a digital temp display on the unit that is exterior to the tank, but you have to look underneath the tank to read the temp.
I am going to stock up on heaters for the winter. I went to the titantium heaters because they come in 300 w, 500w and 1000W units. I use a Won bros titanium heater 1000 Watt to heat up my salt water mixes for water changes. But other than that, I will probably stick with Rena Cal heaters and put two units in the tank. One on each end of the tank. That I think works better.