Which one last the longest?
It is one great question for outdoor enthusiasts ( AKA flashaholics)
I always find reviews and tests from folks who are new to 18650 batteries genuine, and most entertaining.
Average flashlight user doesn't know battery test tricks, and will usually show us a real life 18650 battery performance. Which is very good to get real review data.
They simply charge those cells fully, run them all in the same flashlight (that is important part of this review)...
Lithium-ion rechargeable battery that provides the longest run time is the winner.
Simple as that.
This video shows which li-ion fully charged battery will run the longest in LED flashlight.
Samsung 25R green (very popular battery in vaping and flashlight community)
LG HG2 (good high drain cell, but not many info on flashlight real life usage)
or Orbtronic ORB3400 (well-known battery made for flashlights only)