I have a 300 watt fluval e series, 150w eheim jager, and a 50w aqueon heater (non pro)
the fluval is my least favorite because unless you have very good flow across the heater it will not heat the tank. However when you do get it working properly its very stable. The display is very nice to check the temp with, and its also very easy to adjust the temp
the eheim jager is best performing heater IMO, it heats the tank without any issues. My only complaint is the temp on the dial is way off from the actual temp and you must monitor the temp very closely the first day or two get the proper setting.
The aqueon is "cheapest" heater i have but its only one that i was able to put in the tank, let it adjust to the temp, set the temp i wanted, then plug it in and go. The only downside i can find with this heater is that it does take some time to heat the tank (which really isnt a bad thing because you dont want to shock the fish with quick temperature swings)
if i were to buy one today it would be between an aqueon pro and an eheim jager. I would really like to see more development with the fluval e series before i bought another one.