the bagged carbon in the canister is subject to compacting, muck build-up and channels forming and water not being passed through the entire volume of carbon.
all of those potential issues are eliminated when using a reactor as the media/carbon is slowly peculated it can not get compacted and muck can't build up.
The only drawback/consideration when using carbon in a reactor is making sure it doesn't tumble too much and turn the carbon to powder.
Also the effluent should pass through some mechanical filter material like floss to trap any carbon particles that may escape.
media reactors or fluidized bed filters are the best option for most types of filtration media available today. I have a DIY one running bio-pellets, one running GFO
and one running Purigen.
funny, I currently don't have one for carbon, that's in a canister for now...LOL