Any form of filtration is better than no filtration. In a closed system, exporting nutrients are better than converting to another form.
It depends on what you are measuring against. 50% water change beats mangrove hands down. Poorly maintained denitrator gets beaten by mangrove.
Denitrators are notoriously teadious to optimise. If I were to choose one, I would choose mangrove over denitrator. The more complex the organism is, the better the ability to self regulate. Plant vs bacteria, plant easier to survive from poor maintenance.