If you decide to upgrade in the future go with 510 threading and most every thing will work with it except 808 stuff of course. You are tied to one company with 808 threads and it's more expensive.
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That's not true at all. You can always buy an 808 to 510 adapter. They only cost $3 last time I checked.
Also, in my experience, 510 threaded stuff is far less reliable. There are often problems with the way things fit together, leaking clearos seems to be the norm, and quite frankly 95% of 510 threaded parts are just cheap Chinese made garbage. The truth is, if you're going to stick with high quality parts only, even in 510 you've only got about 5 companies to choose from.
Since he has 808 parts already, IF he wanted to look into upgrades the Halo Triton would be his best offer. Yes, it's 808 which makes it more proprietary, but being more proprietary is actually a GOOD thing. For one, everything he already has would work on a Halo battery (And Halo does have VV batteries as well). Also, Halo parts are made to work as complete systems, not just generic parts which fit other generic parts. Their batteries last longer than Ego with the same mAh ratings, their clearos fit perfectly and NEVER leak a drop, their coil designs are FAR superior to any top coil clearo you're going to find on an Ego, and everything is always made to the highest quality.
510 threading could be described as a Jack of all trades, Master of none. You can be sure that everything will screw together, but have no guarantees on quality, or even if the parts actually work once screwed together.
And then there is the other problem with 510 threading that no one likes to talk about....
https://www.google.com/#q=510+broken+threads