eGo's are regulated to 3.4v throughout the battery charge life. You get consistent
vaping from the Ego. The exceptions are the 1100mah eGo and there's also talk of a 750mah eGo that are both 3.7v batts, although I think the 750mah is a reference to the Riva 750mah battery. Unregulated
batteries charge to 4.2v and drop quickly under load to around 3.7v. They stay at 3.7v for a while and slowly drain down to a 3.2v cutoff, where you have to charge again.
If you use 2.0 cartos, you get good vapor and flavor from a 3.4v batt. Those who like more throat hit will prefer the 3.7v batteries.