I have not used either of those denitrification systems, but have used several others in the past.
IMO, yes they do work, but they are a real pain to set up and maintain.
Denitrification systems work by using anaerobic bacteria to consume nitrates. This requires a very slow flow through the filter, often measured in drops per minute. The bacteria also need a food source.
The problems arise because you must monitor the output water, and test it. Then you need to adjust the flow and in some cases the food source. Too much flow and you don't get complete nitrate reduction, and your adding nitrate back into your system. Too little flow and you get sulphate reduction. This gives you that rotten egg smell.
I would consider the claim by NatuReef that it can "Eliminate water changes" to be pure bull----, and automatic disqualification from my purchase decision, but that's me. Also note that it's very expansive and requires the use of expensive additives to keep it running.
I recommend you save you money on the denitrator and add a decent size refugium with macro algae or an algae scrubber. They will reduce nitrates and phosphates and don't have the problems of control that a denitrification system has. Also, a refugium can be set up as an adjacent tank, and you get a lot of interesting things to watch in a refugium.
