I use GSC-10 for speed (and cadence) mainly because I dont trust the GPS speed readings. When you search for speed and cadence sensor its says 'Speed and Cadence sensor found' and then 'Powermeter found' which means garmin uses GSC-10 for cadence even with P2M. On the other bike I have Bontrager duotrap; havent tested with it yet though.
I'm pretty sure it should take cadence from the P2M. It's a far better value, as it's transmitted as frequently as power. Not just each time the magnet passes the sensor.
I too think it takes cadence from the p2m but would disagree about it being better. Seems like there's a bigger lag between pushing on and seeing the number climb?
I use GSC-10 for speed (and cadence) mainly because I dont trust the GPS speed readings. When you search for speed and cadence sensor its says 'Speed and Cadence sensor found' and then 'Powermeter found' which means garmin uses GSC-10 for cadence even with P2M. On the other bike I have Bontrager duotrap; havent tested with it yet though.