Personally I've been using API test kits for the last 2+yrs. (cheapest tests available) Mainly for ca/alk/ph/no3/no2 and ammonia. They've worked great for me
However I was given a gift certificate for my b-day and today I decided to us it at Dr.FostersandSmiths and bought a Red Sea Max 3in1. Ca/Alk/Mag. I'm sure I could have found something else to use it on but I'm actually more curious to see how big a difference there is between the two kits.