Calculating due date lmp vs. ovulation date

eltar08

Let me just start off by saying yes I know the difference between the 2 and why they differ - that isn't what I am asking.

LMP was 8/21; O was 9/10 (I know because I temped and charted).  By LMP I am 6 weeks along, O 5 and a couple days. 

I have been leaning towards using the O date vs. LMP as I tend to be conservative.  Could you ladies tell me which way you found to be more accurate ultimately?   I won't be having my u/s till end of Oct (either 10 or 9 weeks, respectively), so I won't know how I am measuring for a little while longer.