Torque sensors such as Bosch sample over 1000 times per second for a natural feel, while cadence sensors found in most Bafang kits only detect rotation, not effort, giving an abrupt "on/off" feel.
Why do two mid-drive motors feel completely different to ride? The core lies in the sensor type. A torque sensor measures the actual force you apply to the pedals and outputs assist in proportion to it.
Torque solutions represented by Bosch sample more than 1000 times per second, responding finely so assist arrives with the pedal stroke and feels like an extension of human power. Cadence sensors, as found in most Bafang kits, only detect whether the crank is turning and do not understand how hard you push.
The result is an abrupt on/off character from cadence systems. Once rotation is detected they deliver a fixed ratio of assist, so starts and speed changes tend to surge, and a smooth linear feel is hard to achieve. This is also why many users find "cheap mid-drives" stiff and unnatural.
QERYU engineering chooses high-frequency torque sensing with factory calibration. We use high-resolution torque sensing with thousand-times-per-second sampling and temperature compensation, and we calibrate the zero point of every unit on the assembly line. This ensures every delivered bike has a natural, predictable assist curve.