The answer to that question isn't always so simple as to having an end all be all best 18650 battery, as depending on the mod you're using and how much power you're drawing you need to be mindful and make sure that you are never going over the amp limit of the battery you're using. The easiest way to find out what the most optimal battery would be for your mod would be to find out exactly how many amps you're drawing in the first place.
You can do this by using a simple Ohm's law calculator like you would find here:
http://www.ohmslawcalculator.com/ohms-law-calculator
Just go on that site and use the calculator. Set the voltage to either 3.7 or 4.2(use 3.7 for a more accurate reading accounting for voltage drop and such or 4.2 for a reading with a bit more of a safety threshold) and set the power(watts) to whatever you usually fire at. Set the resistance(r) to whatever the resistance of the coil you are firing at is. With 3 of those 4 boxes filled in you can hit calculate and it will fill in the current(i) and tell you exactly how many amps the mod will be drawing. If the mod you are using happens to be a dual battery mod wired in parallel, you can multiply that amp limit by 1 and a half. If it's a dual battery mod wired in series, then just leave the amps alone and keep them as is like it was a single battery mod.
Once you know how many amps your mod is using go check out the mooch battery ratings charts. Mooch is a third party battery reviewer who gives out really accurate ratings for batteries. You should pick the highest capacity 18650 that is available that stays under that amp threshold. For example the LG HG2 and Samsung 30Q are some of the best high capacity 18650's, but if your mod is drawing over 20 amps it's not considered safe to use these batteries, and you would need to opt for a lower capacity battery with a higher discharge rate instead. That's why it's so important to know how many amps your mod is drawing and to pick the correct battery accordingly. Here's some links to the Mooch battery charts:
Use this chart if you're using an unregulated mod:
Use this chart if you're using a regulated mod: