The difference between a mid-drive (in which all of the force goes through the rear cassette) and a rear hub drive (in which only the pedal force goes through t

The difference between a mid-drive (in which all of the force goes through the rear cassette) and a rear hub drive (in which only the pedal force goes through the rear cassette) is large. Also, most people online report over 2k miles on a cassette. Pittsburgh's hills and more force are apparently good for some extra wear. (Also, a 250W motor is fairly small by e-bike standards. They generally start at 250 and go up from there; 750W is not uncommon.)