I have both on my tanks, AC110's and an FX4.
Big difference is ease of maintaining them.
The ACs are right there, pop the lid and your in the guts. With a canister you have to disconnect the feed and return hose. Then move the can out so you can work in it. Then getting it all back together after cleaning. But dont have to do it as often.
What I have discovered after running them together about a year now is the A.C. does the brunt of the mechanical filtration with its sponge needing cleaned out every two weeks or so. When I set up the FX4 I checked it after a month and it was as clean as the day I started using it. I went 3 months and was nearly the same, almost spotless.
In conjunction these two work great.