I use the power meter, it has a disadvantage where it stops recording power if you stop pedalling (as it should), but the turbo calculates it from the wheel speed so if you do a coast the power and resistance doesn't drop away instantly making it easier to spin up again. I don't care that much about real world accuracy, more about smoothness and the turbo doing calculations tends to jump too high or too low when changing speed. I don't notice any difference in speed for the resistance changing between the two.
I use the power meter, it has a disadvantage where it stops recording power if you stop pedalling (as it should), but the turbo calculates it from the wheel speed so if you do a coast the power and resistance doesn't drop away instantly making it easier to spin up again. I don't care that much about real world accuracy, more about smoothness and the turbo doing calculations tends to jump too high or too low when changing speed. I don't notice any difference in speed for the resistance changing between the two.