The ego booster works on my revolution v2 (though it defeats the bottom feed), lavatube, and provari, all using a pair of 510-510 extenders. I can't test it on my infinity pro because I don't have a long enough connector to fit it--a plain atty won't fire either with those extenders in place.
I think you should be comparing the ego at 3.2V under load vs the 3.3-4.7V you get under load with the booster. On the down side, it really hurts battery life. OTOH, a mod probably won't drop as much under load as an ego battery.