standard ecig
batteries are 3.7v but run around 2XX to rounds abouts of 3XX mah meaning how long it keeps its charge with use higher mah longer use prior to recharge
hv mods the ones higher than 3.7v(4.2 for a short time at full charge) has the beny of what was mentioned before harder throat hit,warmer vapor more vapor
"mods" or PVs that use regular li-ion
batteries beny for cheaper easier replacement HIGHER mah for the most part like 900mah would last much much longer than a regular ecig batt
the 3.7v mods or PVs be again cheaper replacement and could reach even higher mah like the one i have for my pv which uses 2400mah and lasts a long long time (other pv;s that use the same batteries last as long)
there is much more to it but that is the general....keep researching here on the ECF and you will get a plethora of information and from people posting to your thread...