The thing that scares me about cannister filters is I heard that if you let them stop running, like with a power outage, they become a stinking rotten mess really fast. Also it's really easy to change media in a hang on filter and I've heart horror stories about how much more trouble it is to change cannister filters. Maybe my sources are off base. I'd be happy for a solid balanced rationale. I like to make my decisions based on thorough consideration of the pros and cons.