Its so hard to say. Some people recommend sizing up due to foot swelling but i think the issue (for sure in my case) is that my feet are wide and i have a bunion. I have two pairs of the Romy flats from Jimmy Choo that i sized up to a 43 - my feet still get blistered and sore in the toe box by the end of the day. I have roger vivier shoes that i would say do run half a size big - so i buy the size 42 and i need to put the heel grip in the back. The heel grip helps with chafing/slippage but the toe box is still tight. For reference, the most comfortable shoes for me are Chanel - i can walk in them all day long, no matter the style.
I just wore the hangisi flats with hose and walked back and forth a bit they are definitely very comfortable. I think the toe box is more almond than pointy (like the jimmy choo romys) or square (like roger vivier). The almond toe shape is what makes them comfortable - they have already loosened up a bit from the first time i put them on.
I will stick with my size 42 and wear them around the house with thick socks to stretch them a bit.