John, EGO makes two chainsaws (14" = CS1403 and 16" = CS1604). The 14" comes with a 2.5 Ah battery, while the 16" comes with a 5.0 Ah battery. Additionally, the 16" chainsaw has a "slightly" higher Watt motor versus the 14" chainsaw. Now, the 7.5 Ah technically speaking has 3x more power than the 2.5 Ah battery.
Power (Watts) = Volts x Current (Amps)
56V x 2.5Ah = 140 Watts / hour
56V x 5.0Ah = 280 Watts / hour
56V x 7.5Ah = 420 Watts / hour
To that point; I am not certain if the chainsaw will (and/or) can use all that power. What is certain is the 5.0Ah battery will last longer than the 2.5Ah battery. Several owners on this community board claimed that the EGO chainsaw does detect the size of the battery, and therefore, can support more power to the motor - which gives you more cutting torque at the blade. The only way to know for certain is to contact Customer Service to validate this.