I have both both a PH50 and an Abyss and I can personally attest to the statement made by hron61 in the fact that the differences in the performance of these two fine high output lights are minimal.
These powerhouses come up for sale rarely. Now is your chance to acquire a stellar light for a more than reasonable price (spell that a "steal") and from a most respected member of CPF no less! Get it before it's gone before you kick yourself! I paid retail, introductory price which was far above this offering.
Karl