Seachems test are the best imo, they are much easier to use, and last much longer. There is less chance of the test kit being improperly done. Also they are clumped in sets, like iodide iodine tests, and nitrite nitrate tests. The nitrite nitrate test actually enables you to test the nitrite, add a new reagent to the sample of nitrite test, and test the nitrate. So 1 sample, 2 tests. They aren't sold as a group. Even the api test kits only cover the most basic things, and then you pick at choose which test you want in addition to the master kit.