The eGo T is optimized for it's own proprietary "
tank". Basically, they've attempted to upgrade the old obsolete cartridge system. Some people have decent luck with it, but there are a lot of complaints about leaking, etc.
You can use other accessories, but in order to take full advantage of it, you have to buy special parts. That's what it was designed for when they work, they work well.
The kGo has no similar issues. You can get whatever
tank system you want, or whatever carto, etc. It is also a 3.7V battery, as opposed to some eGos which are regulated to 3.4V. I'm not entirely sure what voltage the eGo-T runs at.
My personal opinion is that it's not really worth messing with the eGo-T or eGo-C or eGo-W or whatever the flavor of the day is. Honestly, eGo's are o.k., but they're overrated and most recommendations come from people who have never tried anything else. They have been plagued with shorting problems and charger problems too. I don't know if it's just the odds or a design flaw or Q.C. issues or what, but it seems like every case of a shorted battery due to a leak is with an eGo.
The kGo has every bit as much battery capacity. Get a 1.7ohm Ressurector carto and a tank with a good reputation.
Or get some of the larger cartomizers. See the kGo at Hoosierecig.com You just don't see much problems with them posted here.
If you want maximum battery capacity, an 18650 e-Power will last all day for even a heavy vaper. You can get a 3100mah battery and probably vape for a couple days straight without recharging.