I have personally used API test kits for years, and rarely ever test my water, but I'm personally looking for something better for ca, alk, pH and magnesium.
I like API for the basic test kits.. ammonia, nitrite and pH, but not for nitrate, phosphate, calcium and alkalinity.
I would and do use API for Calcium and Alkalinity as you only need to be in the ballpark
For pH I use a meter/controller I have not found a test kit that I like, I use a controller to dose so it makes sense, the API test kit is no good
I use Salifert for Magnesium but I am going to try some others to find one that may be better
If all you are doing is cycling the tank then API is fine for Ammonia, Nitrite, and Nitrate. SPS and some other corals loose there color if water has miner amounts of Nitrate and Phosphate so if you are going to keep those corals you will need a good test kit like Salifert or Red Sea Reef Pro or you will do what many do and change the chemistry when you see your corals start to brown and not use a kit at all.
I use all the tools out there. Sometimes I just need to know about how the water is and I don't want to spend all day finding the answers so a cheap kit like API can be good and allow you to use it more. Other times you need more precise of a number and if you are going to test it you have to pay up for it. There is no best when it comes to brand you have to rate each kit on its own. Read and learn what the kits range is and what may give a false reading when it becomes to old an may need to be thrown out.