johnnybass,
I've made some mods, laser pointer, from instructions generously supplied on this forum. They worked, batteries lasted somewhat longer than the 510 batteries I had been using and I was torn between going for another bigger battery mod and the ego like you are. Because of all the seemingly satisfied users of the ego, I ordered one from cignot (had heard many good things even recommended them to others with good reports but never purchased from them). I am supremely happy with the ego, cignot and best of all, all of my existing 510, 901, kr808, 510 cartomizers and adaptors to plug any of these things onto the ego batteries all work fine so my recommendation is go with an ego, it's as good as all the praises it's getting and maybe then some. I keep a battery on the charger while vaping the other and in three weeks, that's it, charge it, screw on anything and go as simple as it gets. I don't know but I suspect there's a whole lot more going on inside the ego than most battery mods and the result of whatever circuitry is in there manages the energy in the battery to smooth out the power and make it last the 4 to 8 hours depending on light to heavy vaping. It gives the same results from first puff to the last...excellent vapor production, throat hit (variable depending on liquid), and 510 or better flavor.
Without going to higher voltage and hv liquid, I don't think there is anything in the same ball park as the ego, my opinion of course.
If you like what a 510 does on the first couple puffs, and ego does the same thing longer, like for hours rather than minutes.
Hope that helps.