I'm not a great user of API kits (mine expired 20+ years ago), but I occasionally use them at work, teaching the nitrogen cycle to kids. I have also used test strips, which I prefer as they give much more information. Their only downside to me is their cost - they aren't as cheap per test as the reagent systems. When I have used both and cross referenced, the ammonia, nitrate and nitrate readings have always corresponded. The hardness readings have been the same with strip types as with the very useful API add ons. I prefer strips if I am collecting fish on trips south, as the kit is useless in the field. I end up with extra strips when I return. If anything, because they give more info, they seem superior. It's commonly said here that test strips are inferior to the API liquid kits. Does anyone have anything to back that up? A lot of aquarists I respect here make that statement, but I have never seen anything saying why.