They are accurate enough in the typical range that we want to use. Above 20 ppm the NO3 test kit colors are hard to distinguish, but that level is 'too much' anyway. Between 5 and 10 ppm there is a distinct color change, so getting things in that ballpark is easy.
When I had a LaMotte I compared results of the two kits and they were both reporting the same thing. The LaMotte was able to report say 7.5 ppm (or whatever) while the AP can just report 5-10 ppm, but for our purposes the AP result is just as useful. I threw away the LaMotte because they are expensive (even to refill) dangerous (acids) slow and clumsy.
The AP kits for pH and, less so, KH are also useful
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