There is nothing wrong with API test kits. They don't claim to show results in as small an increments as other kits, but that doesn't mean they are less accurate? Smaller readings like alk of 7.3 or 8.5 are not necessarily more accurate than API at 7 or 8 or 9. Smaller numbers are just that, smaller numbers!
I have 4 tanks and have been in the hobby for more than 10 years. I still test Ca and alk with API kits. I do, however, have Salifert Ca and alk kits as well. I test with API because they quick and easy. If I get a 'way out' reading I retest. If I get the same reading I test again using the Salifert kit. And 99 times out of a 100 if the API kit gives me a wild number I wasn't expecting, the Salifert kit just confirms it and they are always pretty darn close to the same.