They serve different purposes. Filter takes out large food particles and waste, making them unavailable for your corals to absorb, and if you cleaned that out frequently enough, it will also make it unavailable for your bacteria to convert to no3 and Po4
A fuge, on the other hand, does nothing to the uneaten food and waste. It waits for bacteria to break everything down to no3 and po4 and absorbs that while releasing oxygen and maintaining PH.
Fuge generally adds more biodiversity and stability. Filter is more effective if there is a lot of uneaten food and waste, but only if its cleaned out frequently (every 3 days). If your ac70 also has a bacteria media and carbon media layer, then that's also not in the fuge, but can be easily incorporated into the fuge.
Whats more appropriate for your tank depends on your tanks status (bioload, nutrient need, waste profile, husbandry routine,, etc...) ie, filter may strip out too much food and waste if you have a lot of filter feeders or corals that needs it. Fuge may backfire and release waste back into your system is set up improperly or if water conditions are not conducive to chaeto growth. Running both may make your tank "too clean" if your tank has stuff that "prefers a little dirty" water, like if you have softies.