I personally prefer Dvorak because it seems more comfortable for my hands somehow, though I wonder if any of the other popular alternatives have this as well. I think it has something to do with the fact that, as a raptor, moving my ring finger or middle finger down below the rest of my fingers is quite awkward. On Dvorak, q, v, j, and w are the awkward keys and those letters are some of the most uncommon. On QWERTY, x, c, comma, and period are, three of which are fairly common.
I also like how quotes, angle brackets, semicolons, and hyphens are placed since I program things.
My brain can switch automatically between layouts with a few seconds of confusion before figuring it out because I trained myself to be able to do that (once you get good again on one, switch to the other, and eventually switching doesn't require relearning), so coming across public computers isn't that much of a bother.