I've had Won's fritz on me more than others. Some will swear by them. Finnex, personally, seem like solid heaters. My favorites are the Visitherm Stealth heaters. I use multiple heaters so than any one heater will not jam on high and boil my tank out of existence! My two cents is to spread the risk by having multiple heaters where any one cannot increase your tank temperature so much that your tank fries.
Nadir