1. Most shoe styles (i.e. wholecut vs. full brogue vs. derby etc) will fit different, even if made on the same exact last.
2. The shoemaking process can affect fit. One pair of shoes can fit differently than another in the same exact model and size. For example, how long the shoe was left on the last will affect how “hugging” (aka tight) the shoe will be. Also how well it was lasted.
3. The wholecut (by nature of it being seamless) will not only crease but also stretch the most out of all of the styles of shoe.
4. Boots will never fit like oxfords. That being, your heel will not feel as locked in as it does in an oxford. And that is due to the shaft of the boot and needing to make it wide enough for your foot to get in. So, when you try a balmoral boot or chelsea on, DO NOT expect it to fit like your trusted pair of oxfords. And just because it might have a bit of give in the ankle region does not mean that it is not the right size.
5. Monkstraps will not create a great fit for people with low insteps.
6. A cap toe oxford, in theory should crease the least on the vamp (for calfskin shoes). This is not a guarantee however. Another point on cap toes is that creasing on the cap is not always an indication of ill fit, but can very well be an outcome due to your foot (i.e. long vs. short toes) and the pattern not harmonizing. Some caps are intentionally made long for aesthetic reasons and will more likely than not, crease within the cap even with perfect fit.
7. The only way to not have heel slip in a loafer is to have them start off as tight so that when they stretch they will be just right.
8. But heel slip is not always down to fit, but sometimes how rigid the heel stiffener is.
9. Suede will give far more and faster than calfskin. If you are a wide width and cannot fit a certain model in a certain size in the calfskin version does not mean that you should rule out that same model in the same size in the suede version. For narrow feet people, well to be honest, suede is dangerous for you (in terms of fit) as it gives a lot and feels a lot different after a few wears.
10. The more seams on a shoe, the more rigid it will feel.