To me Zimmey has, without knowing it, put his finger on the main point that I see. While some say one test or another is more accurate, I see no reason to really go for precise measurements when, as Zimmey points out, it depends on the light. If one cannot honestly tell whether the reading is 2.0 or 5.0 due to light, I just drop back to what is easy and simple and then set up a standard way to read the colors. I have one tank that I use as the standard light to read the colors. Otherwise I do get different readings. For me it is not a matter of how high/low the readings but how much they have changed from the last time. If my PH has always been 8.0 with one type kit and 7.6 with another than does nothing for the way I want to react. When it works, I leave it alone. If the reading with the same kit changes from 8.0 to 7.6, then I will ask questions. Simple,easy readings that I will do because they are easy beat difficult but precise readings that I might not do.