I'm not sure it's an upgrade. I just think they're different.
The G6 is a KR808 and the Element appears to be a 510. That's the battery connection. Just looking at the specs on their site, it looks like the G6 you have has a bigger battery than the Element.
Battery for the G6- 200 & 280 mah. Battery for the Element is 150 & 180.
You get about 1 hour per 100 mah.
When you say you want to upgrade, what are you looking for?
A cartomizer is a cartridge and atomizer combined. It's disposable.
The atomizer is the heating element and you connect a cartridge to it.
Cartomizers like the ones you are using on your G6 are generally a little easier to use and hold more
juice. But they are disposable.