Upgrade from what?
Ego-sized batteries have more battery life and more power output than the smaller cig-alikes and 510s. If you're new to e-cigs and trying to quit smoking analogs then you do NOT want to be caught with a dead battery and a craving.....so the Egos are a safer bet. Esp the USB "pass-throughs" that allow you to vape even with a dying battery.
Ego-sized batteries can be standard (charged through the top, can't be used while charging), pass-through (see above), or variable-voltage (Twist, Spinner, etc) that allow some control of the power supplied to heat the liquid, changing the flavor and vapor production/temp.
The various brands (and non-brands) of Ego-sized batteries are hit and miss. They all do the same thing. Some can be higher quality than others, but they're all essentially the same. They're available in 350mAh shorties to 1100mAh all-day batteries....they just vary in length. The 1300mAh batteries are thicker in diameter than the standard Ego size but are still considered Egos.
I'd suggest at least one 1000-1100mAh USB pass-through Egos for any new user. Then you won't be caught with a craving with your only quick option to visit the corner store for a pack of analogs.