I use the PO4 and Alk checkers.
I have nothing to compare the PO4 too as most phosphate kits are junk, but it seems to give good consistent numbers. I base that on the fact that I have had it since I started my tank with bare dry rock and have watched the phosphate levels rise and fall depending on feeding conditions and how good I am at keeping up with husbandry.
My Alk checker is dead on, gives me the exact same results as 2 other Salifert Alk kits.
People have issues with the egg checkers, but I believe most if not all their problems are user error. If you understand how the checker works then you can be careful to eliminate any error on your part.
Make sure the reagent is mixed thoroughly, the glass vial is clean and clear of fingerprints and/or dirt, always face the vial the same way inside the checker, and for heavens sake please look up what a meniscus is (proper way to measure liquids in a cylinder) when visually looking at the 10ml line on the vial.
