Well I just put my M9 next to the 10 and played the same music video on both. Both set to landscape to use up the whole screen. Volume wise, they seem the same when set to max volume, but the M9 has a much richer sound making it seem a little louder. No matter how I adjust them, the M9 has a much richer and fuller sound and the 10 sounds tinny. I normally use a bluetooth speaker and pay little attention to the sound coming from the phone. Also the M9 screen seems a little brighter and cooler which I prefer. I will see about adjusting the 10 to appear cooler.