eGo, eGo-C, and eGo-T. Each has an Upgrade 2.
Joye eGo is like saying Toyota Corolla, The "Corolla" also comes in S, XRS...
So the eGo-C (C=changeable) is the little 3 piece
tank system either type A or B that features replaceable atomizer heads.
The eGo-T is the same thing but sealed, apparently you can't change just the atty head, you change the entire cone be it type A or B.
The eGo is very similar but you drip some
juice and keep refilling as you consume (Don't drip and Drive) and like the -T you change the cone when the atty dies.
IMO the eGo came first the got improved as the -T and again improved for -C.
The upgraded eGos have 2 settings:
First setting is unregulated voltage, this means than when the eGo is 100% charged is will produce around 4V and when it's near death some 3.2V.
Second setting is regulated voltage @ 3.7V (can't change this setting and I'm not sure it's exactly 3.7)
Atomizer Type A and Type B.
Type A atomizer cone is more conic than cylindrical, and the B is cylindrical shape
I'll post some links, open all of them and compare yourself by switching tabs or something like that...
Joyetech eGo-T, Tank System starter kits
Joyetech eGo-T, Tank System starter kits
Joyetech eGo-C, Changeable System
Joyetech eGo-C A type atomizer pack
Joyetech eGo-C B type atomizer pack
IMHO you should skip the egos and get a similar one but that has Variable Voltage and maybe a passthrough, it will cost you maybe $30 extra max but you probably get more Mah which means that the battery holds more charge so you don't need to live next to power outlets. And the ability to adjust you voltage is only appreciated once you have a setup you don't like and then it's too late and you end up spending more $$$
just try to ask as many questions as you can, research and compare online.
GL