they are the same exact batteries, they are just wired to fit more cells.
The Difference would be in the Quality off the cells (who actually makes the cells for the battery) Panasonic, sayo, ect.
The battery ratings (Power=enegry/Time) which is reffered to as Ma-h (Mill amp hours) also, volt hours and more.
Plus, how much you Discharge your battery. Almost ALL batteries do not like to be discharged. If you discharge the battery and then leave it discharged, it is very bad for it. So, the quicker you get it back on the charger, the longer your battery will last!
Let me know if you have any more questions!