Olight M20, based on the manufactureres stated runtimes. output is very good, but i think they might have overstated the runtimes on max. check out selfbuilts review. overall an excellent light.
between idealy 2 cr123 rechargeable. But i'd be happy to go to 3 if there were significant gain.
tossing up if i should replace my current HID and EDC's with just one LED or if i still need to go for 2 lights...one for run time one for throw/output.