It’s difficult to say because all riders differ in their needs. However, we are finding that the most reliable one, the lightest one, the kit with the best range and the most generic to fit on nearly all bicycles is the 250W mini-motor kit with the 9Ah water bottle battery. These are geared so have high torque at low speed (below 10 m/h) that is more or less the same as any of the higher powers. This kit also has a superb range, with riders reaching 35 mile regularly on a single charge.If you want high speed,then 1000w,1500w,3000w,5000w gearless motor is better choice.If you want it for you to climb hill,then 8fun mid motor kits bbs02 750w,bbshd 1000w are selection.