So what's the point here? What everbody obviously likes best is to open the drawer with 485's or similar and push one in your circuit. Easy, and especially: without thinking. qed!
where does the "without thinking come from? I thought about 232 (not multinode) IIC (single ended - noise) 422 (maybe, but did not seem to fit) before answering
Similarly I could think of some reasons why 485 would in actual fact be non-preferred (for instance in Ex-harzardous applications).
I doubt very much that you can make a current loop that meet the high impedance requirements for intrinsically safe.

Erik