I have used API, SALIFERT,REDSEA,ELOS AND Hagen master tes kit 10 test in a box a 3 part. And i have to say out of all of them I have found this to work best for me.
1. ELOS, accurate specially in ALK goes down to the half DKH . And PH is really easy to read. Po4 is nice to,MAG is a pain in the but thats how it is no matter what brand.
2. Red Sea, accurate and fast.
3. Salifert little to long and some times more complicated than needed.But really on point!
4. Hagen 3 part, great but Ammonia is kind of whack. But PH is kind of easy hard to tell the purples apart with the dark blues.
5. API nice and fast. Great for basics but when you get into harder species you need more .
Hope this helps.