Prior to having DD I worked in perinatal trials and the rule we used was there had to be more than 10 days disagreement between LMP and u/s dates for us to use the u/s over the LMP (don't collect ovulation dates). Also, we only used the u/s if it was done at <24 weeks. As far as I know this is the same rule the OBs involved in the trials unit used in their practice.

Your OB sounds reasonable letting you make your own decisions. Good luck. I hope you beat the induction.