My local bike store says they can work on (plug into computer to diagnose) Shimano and Bosch motors but not others. Should their comment lead me to buy a bike with one of those motors and avoid others (Tongsheng, Bafang, etc.)?
Best bet is to buy local
if at all possible, and Bosch, Shimano, Yamaha, Brose are all in a different/higher class (much smoother, more sophisticated sensing, likely more reliable ), than Tongsheng or Bafang. Although you could nearly buy 3 Tongsheng's for the cost of a replacement Bosch, you'll find your shop will be worth its weight in gold when it comes to potential future trouble-shooting, and this goes beyond just the motor, and helping you take care of your ebike. Ebikes being both mechanical, and now electrical, present entirely new challenges for the average consumer. They are likely to be pretty reliable, since they are still relatively simple devices (compared to say a car), but eventually anything with the type of stresses and wear and tear a bike will take is bound to need service. Sometimes it seems like consumers expect these to be entirely maintenance free and trouble free, like many appliances can sometimes be, until they simply break and you buy a new one. Bicycles have been known to last years, despite the consumer not lubing chains, or doing even the most basic care. Ebikes you wont be so lucky, since there are more forces involved, and introducing more power is going to create more wear on a lot of items. Tires and brake pads may need to be replaced more often. Same thing with chains. Part of it depends how you ride it. You may find yourself riding considerably more frequently, and even further than a regular bike if you were recently riding that.
The uptick in phone calls each year, from consumers who bought 'brand x' on line, and who were largely unable to do even basic maintenance, has increased exponentially. The call usually starts with "Im stuck and can't find help with x." Or "I'm in a predicament" as no one will work on my brand x ebike. The local Trek store, said they've altogether shut down taking in any other brands of ebikes, despite repairing and taking care of any brand of regular bike that needs service. They sell ebikes. But they have learned the challenges, and frustrations of dealing with the on-line firms when they are trying to help a customer fix their on-line purchased ebike. Its a no win situation for them or the consumer, as they never recoup all the hours spent, trying to solve what would be easy problems with their own brand, and the consumer simply can't believe something would cost that much for service, or they refuse to pay for all the hours spent, due to such poor aftermarket support by many on-line brands (if there is any at all). The Trek store got very specific and rattled off a number of 'big name' on line brands and the issues. I knew he was truthful, as I have had the same type of support experiences with those same firms. Its sort of sad, as the consumer gets the short of the end stick, and it can sour the entire ebike experience, misleading them to believe the industry isn't ready for 'prime time' though it most certainly is. Save yourself the eventual headache, and sometimes immense frustration, and buy local if possible.