best heater I ever used? cheapest heater I could buy on ebay. think I paid like 7 or 11 bucks for a 250 watt. used it for about 2 years before I took the tank down. never had an issue out of it. I actually had 2 in the sump, both same size set to the same temp.
IMO what makes a heater better is how well its sealed, and how durable it is. well, on these cheap ebay heaters I haven't had any leaks so apparently theyre sealed pretty good. and I keep my heaters in their own compartment in my sump where they cant be damaged. I also use heaters that are bigger than I need and I always use 2. this way they are never overworked, they don't have to stay on long enough to crack or break open. worst heater I ever used was marineland. paid like 20 bucks at my lfs when I should have just bought off ebay.
however, with any heater I recommend a controller. whether it is apex or finnex doesn't matter. just use a controller to control the temp.