As some have mentioned - 18650 - is a battery format. So when thinking about choosing bicycle lighting think in terms of how you will use the lights - not just battery specs or lighting power.

Many of the long time forum readers have multiple styles of lights are that over powered and redundant because they understand that different situations will require different lighting.

Recently I used Blackburn "click" lights - they use the tiny CR2032 battery. But they are perfect to get me down to the Pizza place and back safely. On my race-ready road bike.