But as in all things, people differ, but when using a wood routing table, you save a lot of headaches if you consider the 4' side of a 4x8 table to be the X, not they Y.. (My opinion only..but thats pretty typical. )
Art
I'll disagree here. On large machines I don't believe it's typical at all. I run and program a large commercial router (which happens to use X as the long axis). Other than your door example, Imo most other examples would be the opposite. Especialy when cutting parts out of large sheets. Typically, when drawing your parts in a CAD program, you'll draw them with the longer side on the X axis, left to right. This makes more sense since it fits on the screen much better. And this translates much better when the machine is setup the same way. Imo, it's a very simple task to rotate the door in the CAD program.
As you stated, it's always the users choice, but I see confusion amongst beginners with this topic all the time. Imo (and most large woodworking machinery manufacturers), the axis on the gantry should be Y. I think making that a "standard" would be a benefit with support issues, if everyone was always talking about the same thing. Or at least let people know that making the gantry axis X is deviating from industry standard, so they know what to expect.
Just trying to minimize confusion.