Aqueon Pro vs. Eheim Jager and temp alarm system

[mattcham]

Aqueon Pro vs. Eheim Jager
These are the 2 highest rated heaters on amazon.com.
Any suggestions on which one is less likely to cook my fish?

Also, does anybody here use a separate temperature sensor and heater controller that will automatically power down the heater if temp gets too high (due to heater failure)? If so, which brand/model are you using?