Problem is, no two peoples' feet are the same. Even if you take the same size, there will be subtle differences. As a bloke, I have paid over 80 quid for a pair of shoes, only to find another pair I bought for 20 quid were more comfortable! It really is up to the individual sadly.
What a sensible post. Of course not every shoe will suit every foot.
I can remember in the 1970s being crippled by my Scholl wooden sandals but persevering beyond reason because everyone kept saying how comfy they were and how good for your feet. I've learned since then!
I have had a couple of pairs of Flyflot mules and they have been VERY comfortable. Apart from my Emu boots I don't buy shoes mail order as it's very important to try shoes on before you buy. I think the size depends to a large extent on the style. If the shoe is wide you can possibly get away with a smaller size than if the style is narrower.