what device do you use ?
i feel the difference if i try ego with leo , leo got more power but it's still @ 3,7...
some device has amp limit, like LT doesn't matter you use on higher voltage it produce the 'safe' voltage, like DC ( 1,5 ohm ) if you put it on LT @ 6 V , its like @ 3,8- 3,9 on other device ( wich doesn't have protection like buzz pro or vmax ) ...
i think provari v2 has that limit ( 2,5 Amp ), if you compare with buzz ( 3 Amp )...