The capacity of the LiPo battery is measured in mAh . mAh basically means the current that you can extract from the battery for one hour.
For example, for a 1000 mAh 3s battery, it takes an hour to fully discharge if a constant 1A current is drawn from it. If the current draw is doubled to 2A, the duration will be halved to 0.5 hours. If you keep pumping 30A, this battery pack can only last for 2 minutes. Increasing battery capacity may increase flight time. In general, it is best to get the highest possible capacity battery. Higher capacity can also provide you with higher discharge curr