I've only used the Tunze ATO. From what I can tell, the thing that usually goes first is the pump. I bought my Tunze used and it went for 5 or 6 years before I had to replace the pump. The Tunze has some electronics so these will eventually go bad but mine has been going for probably 10 years. Also has a power supply so that can always go out. So, I guess what I'm saying is it will depend on what you are looking at and how complicated it is and how much it relies on electronics. I'm an admitted Tunze fanboy so that is what I will always recommend.