I am using an aquamedic one (not sulfur based) and my buddy in the bay is using an h&s sulfur based nitrate reactor. They both works however, mine does clogged up a lot because of the slow drip rate. I rarely see any PH drop however, if the flow rate is too fast then OPR number will drop (assuming you have enough bacteria build up in the reactor, that lovely smell :lol: ).
When I had my tank up for a year there was so many ways I tried to reduce nitrate in the tank but nothing was able to lower it to an acceptable level where my sps would color up nicely. Reading a lot of thread regarding these reactors and a lot of folks wasn't too happy with them and said that it's a waste of money. However, I found an individual who had lots of success with his reactor and through a lot of PM had helped me setting up mine to operate the way it should and it did.
Just note that you might have to adjust the reactor more than you like to because of the slow drip rate as well as the nirate produced in your tank is changing from time to time depending on your bioload. I do have to adjust mine all the time, now I just let it drip for a day or two until it clogged up and then let it sit there for a week or two and adjust for it to drip again since I can't detect any nitrate with my Salifert or Elos test kit, so I am not too worry about getting it to work consistently.