I have quite a few mods for both batteries, and there simply isn't a 26650 battery that can compare to a Sony vtc5a. There is very little benefit to a 26650 battery. Having used them both pretty extensively, i can't see any reason to choose a 26650 mod other than a preference for bigger size. I use alot of 30mm rdas, so I like the bigger diameters that come with the bigger 26650 tubes. None of this should apply to a box mod though. At the ohm ranges you are planning on using, you would be safe on a single 18650 mod even. There wouldnt be much headroom left in the battery, but as long as you are using a quality battery, you would be more than fine. The only quality 18650s are made by LG, Samsung, or Sony. If you're using anything else, then you're doing it wrong. I always recommend sony vtc5a batteries because they have a great amp rating and relatively decent run time. With a triple 18650 mod with 3 fully charged vtc5a's, you would be safe building to .05 ohms, pushing 75 amps total. Not that I recommend that, because your mods mosfet(s) can't possibly handle 75 amps, but those batteries wouldn't even break a sweat with that configuration. As far as the wire upgrade inside the mod, for only $10 you'd be a fool not to. It shouldn't make too much of a difference, and may not even be noticeable to you, but that is a very small gamble for something you will use so much. I certainly would.
