Well, there are a bunch of different ways to look at it.
I, myself, plan on carrying a 33" spare. I plan on changing the tire in the bush then swapping the small tire to the front once I get to the trailhead and then continue on my way home.
If you try to run two tires of a large size difference (say 2") you will cause an automatic locker to go berzerk. I found this out a couple years ago. It behaves just fine until you let off the gas. So, to bring it to a stop without horrible banging you must use some throttle while braking.
I probably won't even carry a spare once I get beadlocks. Just continue to carry a bunch of tire plugs and patches.