Hi I have been looking at getting a new better filter for a 75 gal tank. I was wondering about a external canister filter. Any opinions on this type of filter would be greatly appreciated ;)

See my response in your other thread.

Pros of canister filter:

More filter material
Ability to put in whatever types of filter materials that you want
More capacity
More room behind the tank

Cons of canister filter:

Always a risk of leaks [Drill a 1/16" hole an inch down on the intake tube so that, if there's a leak, the tank will drain down to the hole and no further.]
Hard or even painful to open and cumbersome to deal with
Has to be sealed just right to not make noise and to not leak
More expensive