As Kurt stated it is not a matter of actual numbers accuracy as it is interpreted accuracy. Test strips could be used in emergency situations or even new shipment arrivals where you need to know if there is NH3
present prior to acclimation and remedy; however, detailed results are left to the imagination. Liquid tests, imo
, are better by far, but does not stipulate a proper readout in the final "drop" phase. In other words, how much of that final drop was overkill or even underkill? If you can, use a color wheel over block cards. The final outcome is guesstimation based on perception once again. Titration is better if using syringe method, but still there is a % of error (from what I've been informed, around 10%). Personally, as long as it is serviced, reagents are properly stored, and your blanks are standardized, I prefer digital and if you can afford...Spectrophotometer.