For some people a wide board makes the difference between heel and toe drag, and not being able to fully carve and having no problems. Most physical differences may not seem that significant...but they are, because you have to take into consideration alot of things like sidecut, radius, etc etc.
Anyway, to find out if your boots are properly fitted or not, strap just the boot into the binding, and rock it onto the toe edge and see how far that goes. If you can rock it up to about 90*, you it's fine. If it's significantly more or less, then that's a bit of a problem.