No the sump acts as a filter.
I've only ever heard of canister filters being bad news in a reef personally.
A sump can really do what you want, filter the water. Provide a place to hide your equipment.
A refuge with a sand bed of 4-6 inches deep some live rock and macro algae is the best filtration for a reef in my opinion.
Basically a sump is normally customized to do what you want.
Personally my sump is just a place to hide equipment off main tank. But I should have gone refuge with it IMO