I tested a few of the Pro kits about 3 years ago. The only one that I found to be accurate were Ca and Mag.
Clown-Keeper99, I think your LFS is playing you. If tank water sits for too long, it shouldn't be used for testing. So sending it to a "lab" for testing is probably just a publicity stunt. I could not let a LFS test my water.
Ca, Mag, and kH are the others I have interest in. I like the Titration tests better then the Colorimetric and I see Red Sea has test that Salifert does not.
I have one LFS that I'd trust, but the vast majority I wouldn't. I mainly use SeaChem and Salifert for testing, as well as probes for pH. I'm not a huge fan on API kits. The SeaChem kits are mainly the colorimetric, but I like that they come with a testing solution.