Yes. the 52v/11.5Ah battery is a 598 watthour battery. The 48v/14Ah battery is 672 watthours.
Watthours are how you rate the true capacity of a battery. If thats hard to understand. Think of a glass. Voltage is how tall the glass is. Amp hours is how wide the glass is. Multiply them together, and you get how full the glass is. Thats watt hours.
Depends on battery type. Assuming the 52V is lithium and the 48V is lead, there's going to be a lot of difference. 11.5ah 52V lithium will like have twice the range as the 14ah 48V lead. If both are same chemistry, there won't be a lot of difference. Would need the watt hour specs to be specific.
Or it could be that one battery is a "48v" 15s lifepo4 that charges to 52v
And the other is a "52v" 15s lifepo4 that charges to 52v. Cellman for one, uses fully charged voltage when describing his packs. Most use nominal voltage which is close to the same as the minimum voltage when discharged.