Lots of talk about fit lately - which, for a newcomer, must be utterly maddening.
Nothing beats try-on, and there is no doubt that individual preference plays a part, as do other variables (e.g., insoles, thickness of sock).
Moreover, a person can try on the exact same model in the exact same size and may like how one pair fits and not the other ....
I consider myself TTS US9.5D (and UK8.5E). I wear a thin insole (not ortho) in all my dress shoes (always have, always will; I like how it feels). I don't even know the brand of the insole because it is so old and just keeps on ticking. But I do not wear an insole in any of my loafers, as I find the fit to be better if I don't. So, with all of that said, my sizing usually shakes out as follows:
9C - Van (slip-on)
9D - barrie, tremont, trubalance, plaza (shoes)
9.5B - aberdeen (slip-on)**
9.5C - M-58 (like barrie), M-75 (like Plaza)
9.5D - aberdeen (lace), plaza (boots), grant, hampton, snap, leydon
f I get a 9.5D in an aberdeen slip-on, my foot damn near comes out of the shoe with every stride given the amount of heep slippage. Even the C width has too much heel slippage for my liking.
But even the above is not without certain exceptions, as I have M-75 and aberdeen models in 10C, I have hampton and aberdeen models in 9D, I have a snap model in 9.5C, and a Barrie model in 9.5B.
JEBUS! Talk about throwing a wrench in the gears when it comes to "The Alden Last Rules". God speed new-comers.