I had the exact same issue with these boots. In my case, 9.5 felt very uncomfortable and 10 felt like it's not snug enough. Ended up returning the boots.
I am size 10 US in my regular shoes and I got Nike Kaijus in size 10. They are softer than DC Judge Boa and have slightly larger footprint. I don't even feel like I'm wearing snowboarding boots when I am on the mountain. I tried all major boot brands (Salomon, 32, Burton, Ride, K2 etc) before deciding.
Not saying you should get the same boots, but you should probably try on some other boots to see if you can find a better fit.