Beetle regardding outboard xo's didn't Tom say something about the length of the wire to the drivers form the xo being significant to the design? Maybe not. If there is no adjustments for design criteria going to an outboard xo I would rather get outboard if it has the most sound advantages.
That is true that given the same configuration, having an outboard xo will require a slightly longer wire run from the outboard outputs to the driver inputs.
But if you're going outboard, you will have to modify the binding posts to bi-wire anyway. And if you're brave enough, you could place the bind posts on the back panel right behind the drivers (by drilling a few holes) which will shorten the wire run to the point which it will not be an issue.