P10 and T600 are the same design product, but P10 is OBD2 Speedometer, and T600 is GPS speedometer.

P10 OBD2 speedometer:

OBD2 means it will use OBD2 protocol via engine to get all data. Therefore, it has many functions:

speed, engine RPM, water temperature, voltage, odometer, instantaneous fuel consumption, average fuel consumption, driving distance measurement, driving time ,low voltage alarm, high water temperature alarm, over speed alarm, engine fault code alarm, eliminate the fault code.

However, it can only works on some latest cars.

T600 GPS speedometer:

GPS means it collects speed from GPS satellites. Therefore, it can be used on any cars, universal! However, it has some limit functions:

speed, time, compass, altitude, voltage, single travel mileage.

Therefore, it’s a choice for those cars which can’t work on OBD2 devices. Eg,  old cars, italy or french brand cars, pick-up,Oil and electricity mixing, and diesel powered car.

Similar as P12 OBD speedometer and T800 GPS speedometer; C500 OBD hud and T900 GPS hud. 

However. P12 and C500 functions are a bit different from P10, pls kindly check the product description on aliexpress directly.