If you want us to mark which one we prefer, I use the AP kits, I don't like the master kits as there are many things I don't need in them, but use AP test kits for all of my testing. My reasons are quite simple.
1. AP is everywhere, and usually inexpensive as test kits go.
2. I've never had a problem with the AP products, and even have some that are 7 years old and still accurate (not reccomended to use them that old but mine test good against new kits)
3. Good variety of products.
I have not used the others, so cannot say if they are better or worse, Or if there is any difference. the only thing I don't reccomend is the quick strips. I have used them and find them to be quite innacurate and hard to use.