Originally Posted by
Bezalel
The 6703 spider is a double and it uses a triplizer middle ring so you can't mount the inner ring without the middle one. Regarding the crank arm, the 6700 and 6703 use the same left crank arm.
The Garmin Vector looks better but it costs almost twice as much (but it measures both legs).
I've been using Vector on the Captain's crank for about 3 months now. Other than a couple of setup glitches, it's worked fine. I can't see any difference in the data from the Quarq on my single bike.
The Stages Power meter is supposed to be improved with its second generation of software ( see DCrainmakers review).
I'd prefer the garmin over the Stages because:
1) Vector appears to be a more mature product from a mature company, wheras Stages is a startup. Virtually every new power meter design released has had some initial problems. All the testing and delays Garmin went through bringing Vector to market gives them an edge in that department;
2) Vector gives you actual power from both legs, not an extrapolation from 1 leg.
Obviously cost is an issue, but if you're going to have to make changes in the drivetrain to utilize a Stages crank, the cost savings get smaller.