What are the pros/ and cons of the two types?
Ability? Noise level?
-Won't leak water out of tank if it overflows
-Looks more aesthetically pleasing
-Can be noisy
-Doesn't leave a whole lot of room for extra media
-Can be pretty pricey
-IMO, easier to clean
-Leaves more room for extra media
-Looks chunky hanging off the back of the tank
-Will leak water out of the tank if it overflows
But it really all depends on the brand and how you maintain everything.