Yes essentially it is a much bigger battery for a 510 type atomizer. The standard ego's have a battery capacity of 650 mah, the "mega" or "XL" versions have around 900 mah, compared with just 150-180 mah on a standard
new 510 battery (and they do lose capacity over time). The battery on a 510 has never really been sufficient for the level of power drawn by the atomizer, and IMO the Ego is a worthwhile upgrade just for that reason.
There are a few more recent developments which the ego can use.
- Low resistance 510 atomizers. These run hotter, draw more power and produce more vapour than standard atomizers. Due to the level of power they draw, it is not advisable to use these on a standard battery, but they work well with the ego.
- New larger ego specific "mega" atomizers. Although they use the same connector as the 510, the atomizers are a different, wider design. They have a much larger cartridge, and come in two varieties - the "cone" type and the "cylinder" type. Be aware you have to use the correct cartridge for the correct version. The "cylinder" type can hold 2ml
juice in their cartridges.
- There are also large cartomizers available for the ego.
Hope this helps