My Tremont experience is about as small as I can get in the toebox w/o sizing up (but still very comfortable). The shape is more U-shaped than the barry, but not as much so as the Leydon (which I commented on a few pages back). FWIW, I've also felt it to be a "flatter" sole, as in not offering as much arch support as others. I have a Tremont Balmoral, so the lacing is different, but my foot is very snug inside. Not overly tight by any means, just well wrapped.
^^ I have never worn the Tremont. I am a solid 9 in the Aberdeen and the Barrie is too big. I just purchased a 9 in the Tremont - Argentino give me your thoughts, please.
If you are a solid 9 in Aberdeen, I would go with 8.5 in the Tremont. However, it really is a tweener if you poll people that have them (half will swear by TTS and the other half will say size .5 down). I think you just need to try two sizes and figure it out for yourself. Good luck and let us know how it turned out for you!