You mentioned an accident that injured your legs. I would think going for higher motor torque would be a good strategy. The Vado 3 develops 75Nm where the Vado 5 is at 90Nm. I ride a Vado 5. It climbs any of our steep local hills. I think tou'll notice the difference.
I test rode a Giant with the Yamaha drive. It felt weaker than the Vado 5 to me though it had a double chain ring which helped. It had an 80nm torque rating. I haven't ridden bikes with the Shimano or Bosch drives but their torque specs are lower as well; https://shopsandiegoflyrides.com/bl...log/84011011-bosch-vs-yamaha-part-1-the-motor and https://electricbikereview.com/forums/threads/shimano-steps-e8000-torque-power-values.29368/
Good summary of the difference in ride feel between Bosch and Yamaha... thanks for posting the link.
Very similar specifications between both manufacturers. Although the Yamaha system does have a little more torque, in fact we list a continuous torque figure but it will actually peak at a whopping 80Nm! The Yamaha system offers slightly more assistance too and the power comes in a little earlier than the Bosch motor. Although the power curve is smoother on the Bosch system. Yamaha call this instant power ‘0 cadence’, it is there right from the off. Other differences: The Xduro line is also considered a little bit of a step above in terms of builds. So you'll generally find similar models to be equipped/specked out a little better in terms of overall components used.
Our overall feedback: We find that customers coming from a more traditional cyclist background tend to gravitate to the Xduro/bosch system as the system feels smoother and more like what they're used to on a traditional pedal bike. That said, if you're doing some steep climbing or a touch on the heavier side, then you'll find the Yamaha system will not disappoint. For where our shop is located, this system tackles the steep grades around here better than just about any other bike on our floor.