In my case, I use both Bio Clean and Bio Digest on alternate weeks.
If using just 1 product, I would say go for Bioclean. Main reason being it also has trace elements which are actually good for your tank. Just to explain further, Bio Digest is just 1 product, Bio Clean is Bio Digest and Bioptm combined. In the pack of Bio Clean you will get 15 vials of Bio Digest and 15 vials of Bioptm. Just need to dose 1 vial each per 2 weeks.
Bio Clean/Bio Digest can be used with AZ NO3. What I did was in the first week, I dosed AZ No3 at the full dosage and used Bio Clean. 2nd week, I dosed Bio Digest and reduced the daily dosage of AZ NO3 by ard 20%. 3rd week, test the nitrates. If the nitrates are maintained or have reduced, reduce the dosage of AZ NO3 by 50% and dose Bio Clean. 4th week test nitrates again. If nitrates are maintained or reduced, stop dosing AZ NO3 and dose Bio Digest. Subsequently for the 5th and 6th week, I just dose 10ml of AZ NO3 once a week. If the tank does not turn cloudy, then I stop dosing AZ No3 and just rely on Bio Clean.
When using AZ NO3 only, my tank was at 10-25ppm nitrates which was down from 50-100ppm before using AZ No3. After using Bio Digest/Bio Clean and stopping AZ NO3 dosing, my nitrates have stabalised between 2.5-5ppm.