...you asked...
I think the Joye eGos are the weak sister of the clan...around 3.2-3.4 output(I've been told)...the Rivas at around 3.7 and the KGOs at 4+...and battery replacement for the family run around 12-20bux depending on size and vendor...batt life should be in the 6-10+-hr range and they have around 2-300 charge cycles in them...
...the E-Power puts out a regulated 3.7v(supposedly) so it should give a more consistent vape...also, since I am using hi-drains batts, they should come up to voltage/amps/watts faster, giving a quicker vape and should last 12-18hrs+-(I hope) and have many more charge cycles to them, meaning they will last and live longer... plus replacements are 5-9bux...I am also hoping, because the E is a bit longer and heavier, I won't hold it my hand constantly and will help to cut down on my chain vaping(a sure pie in sky hope)
madjack
p.s. I was changing Riva batts out every 5hrs rSo and going thru at least 3+batt changes/day, I hope to cut that down to one change/day.....mj