I have regs from each of these manufactures.
My Mares is V16 Proton and I have issues with it at depths over about 130, I therefore use it in the pool and in the keys or other tropical settings (I haven't tried it in the cold, becuase after the previous problems I haven't tried it in cold water)
I have an Oceanic Delta, that I don't let touch the water. It has free-flowed on me several times, and I have several other friends with the same reg that have the same problem.
OTOH I have the APEKS AXT 200 and I can't say enough good things about that regulator. Cold water, deep, it does it all.