When choosing an electric bicycle, the number on the battery label matters, but it is only part of the picture. In Bosch's comparison, the new PowerTube 360 holds approximately 360 watt-hours of energy and weighs about 2.1 kilograms. The PowerTube 720 holds about 720 watt-hours and weighs roughly 3.9 kilograms. In this pair, twice the nominal energy comes with about 1.8 kilograms of extra battery weight.
Both batteries fit inside the bicycle frame and belong to Bosch's smart system. The smaller unit allows a slimmer bicycle profile and may suit frequent, shorter city rides. The larger one brings more stored energy for days when distance or climbs call for a wider margin. Neither is automatically the better choice: the rider's routine and the design of the complete bicycle both matter.
Watt-hours are not a precise range forecast. The assistance setting, terrain, rider effort and conditions all affect how far a charge will take you. A 720 Wh battery therefore does not guarantee exactly twice the distance of a 360 Wh version in real riding. A useful comparison puts energy capacity beside weight and intended use, rather than treating a single specification as the whole answer.