so there will be no difference between the battery i use, as long as my build the same?
cause a friend of mine said it will be difference in firing power if i use battery with more amp.
Amps are "pulled," not "pushed." The amp rating tells you how many amps you can try to pull from a battery before it causes an unsafe situation. The higher-rated battery can handle a higher demand than the lower-rated one, but the rating itself does not determine the power output. Both batteries will charge up to 4.2 volts at full charge, and drain to around 3.5 when you will need to recharge them. The difference is that the HB6 can be safely discharged at a faster rate (you can "pull more amps" from it) than the 25R. Using a 2.1-ohm atomizer on a full battery will draw only 4.2v / 2.1Ω = 2A, so you're well within the safe zone in either case. The higher-rated HB6 has a lower capacity (measured in mAh or milliamp-hours) in exchange for its higher amp capagbility, and so since you don't
need those extra amps that it is capable of dishing out, you're probably better off with the other one since it will last longer in between charges. A current of 1 amp, sustained for a total duration of 1 hour of firing time, uses one amp-hour or 1,000 milliamp-hours (mAh) of electric charge. Using half the current for twice as long (half an amp for two hours) or vice-versa (two amps for 30 minutes) uses the same amount. At 2500mAh for the 25R and 1500mAh for the HB6 (I'm not certain, but I believe those to be the capacities of those two batteries), the 25R has about two-thirds more capacity than the other one, so long as you don't need to use that capacity faster than the battery can deliver it.