Normal ego batteries are only 650 mah.
That is not accurate, Joyetech eGo batteries are widely available in 650, 900 and 1000 mah versions. The 1000 mah is also available in a passthru version (which the Kgo doesn't have). Also, the new eGo C Upgrade version batteries have an unregulated mode that is essentially the same as the Kgo. Finally, the eGo-C Twist model that is expected to be released in April has continuous variable voltage from 3.2 to 4.8 volts (which the kGo also doesn't have).
The higher voltage in the Kgo will allow more wattage and really helps when you want to use low resistant cartomizers as the normal ego can barely handle them well.
Also not accurate, as Boge LR cartos, EMDCCs, etc. are widely used on eGos. Indeed, Joyetech even makes LR attys for both the eGo-T and eGo-C models.