I have not used either but have seen both. I don't like the bulky appearance and reduced cornering clearance of the Powertap pedals. With their clamp-on pods, the new Vector II pedals are significantly easier to install than the originals but still should be done with a torque wrench. Garmin now includes a crow's foot with the pedals to facilitate this.

As far as advanced data, I don't know of anybody that has come up with a way to use it that has shown any benefit.