Comparing what I’m reading here with my own experience I reckon it must depend on what shoe/boot you’re after.
I’m a size 7 exactly on my right foot and just over a half-size smaller on my left. I opted for a pair of Quests in size 7.5 (a foolish web order) but regreted it within miles of proper walking as opposed to simply wearing them around the house; they were much too small, even on my smaller foot, which was especially uncomfortable when descending as my toe bumped the front of the boot which would not only cause a callous given enough time but would also damage the GTX lining (not that it functions that well anyway). I’ve ended up buying a pair of 8.5 which are just right – nice and roomy on the toe box and snug in the heel area. Also bear in mind that I prefer to wear base layer socks as opposed to the thicker type of walking sock that many folk go for and you’ll get an idea of the weird sizing of some of their range and I know I’m not alone with that experience.
My suggestion is to try them on rather than gamble on getting a good fit by guessing/asking on a forum.