The eroll uses the same atty as the ego. The ego upgrade (if that's the one you have) when in regulated mode (white light), however, is regulated at 3.3 volts while the eroll is regulated at 3.7 volts. The upgrade in UNregulated mode (orange light) with a fully charged batt gets 4.2 volts for a very short while and then mostly 3.7 volts until its about 3/4 drained and then drops in increments down to 3.2 volts until it needs a charge. Volts, and consequent heat, are going to affect flavor depending on the temp required for different flavor molecultes to be vaporized. So with any setup voltage counts greatly where flavor is concerned. Then, of course, there's the delivery factor. Most cartomizers are going to delivery more flavor than something with a small wick like the eroll, clearomizers and other tanks. I've heard tell the best flavor delivery is a cartomizer in a tank and that makes logical sense but I haven't tried it. Anyway, I'm trying to say there are many factors that affect taste so you can't really compare using just the battery type. But, with a clearomizer on it, the ego in [Iunregulated mode/I] should taste pretty close to an eroll. I only use cartomizers on my ego so, yes, that way unregulated mode (which will drain it quicker) there is more taste depending on the juice I'm vaping.. (remember different ones require different heats.) But with another juice, in regulated mode on the ego with cartomizer, I get less flavor than the 3.7 volt eroll. Hope that helps and I didn't make it too confusing.
