I had a Tronic heater last me 3 years heating a pond outside until a raccoon took it out of the water and banged it on a rock until it broke. Keep in mind that was the second time I found it out of the water. The first time it had singed the grass and turned itself off.
I like the Won Bros. titanium. The controller is outside the water which is nice also. The titaniums from fosters and smith suck though. i can't think of the brand right now , but i've had both of them die on me.