Which US would be most accurate??

Dreama

So the first day of my LMP was 5/15. Though it did come on 4 days early it was still a normal period (heavy bleeding/clots/cramps/6days)! First US was 6/25, I was measuring 6w4d. According to my LPM I should’ve been 6w1d. 2nd US was 7/26, I was measuring 11w BUT my OB didn’t change my date, he actually advised me to stick with the EDD of my LMP which would’ve made me 10w1d. Which US would be most accurate, one at 6w or one at 10w? Just curious