Selecting the BEST single CR123 light would depend on my primary use.
Is is for general purpose, around the house...
Is it for Traveling, Camping.
Will it be used in a Self Defense situation, as well as General Purpose.
Here are my thoughts.
I have and use a Sure Fire E1e Executive Elite. I carry it daily around my place and I never leave home without it. I like it so well I have a brand new spare, I have been using it for several years.
I like Incandescents, but I might consider the E1L for its longer run time.
Also the L1 is brighter than the E1L, which is better for a self devense light, and it still has a lower setting for General use.
The E1B is worth a look, especially if you wear a suit as it appears smoother than the others, ie easier on your clothes. Also its 2 way clip might prove handy.
It has a good runtime on its high setting and a very good runtime on its low setting.
These four would be the ones I would recommend you consider.