The CT comparison should reveal a large discrepancy, assuming you warm up your CT before comparing, but I wouldn't count on the CT revealing a small discrepancy (e.g., 10W). When I first got my CT, I compared the CT watts with my PT watts after warmup and using the CT procedures for setting press-on force and the rolling resistance calibration routine. I found that the CT was off by enough (although I can't remember the number now) that I decided to set my press-on force more precisely and not rely on the CT rolling resistance calibration routine. So, I machined an adapter out of aluminum for using a precision torque wrench to set the press-on force. That procedure allows me to get within 1-2 watts of my PT, but I have to change the torque force slightly as my tire wears. Also, I have run MAP tests for other cyclists on my CT and I have found huge variances in the amount of torque force depending on what tire they were using. When I say huge, I mean a range of about 40lb-in - 75lb-in, depending on the tire.
!
