The salient difference for me is that the real one has maximal impact. Many actions in it can affect anyone in a lower world, but not vice versa. I'd like my decisions to have as much effect as possible as a general principle, I think (not the only principle, but the one that dominates in this scenario).
This is pretty much why I'm comfortable calling being in the highest possible world a terminal value - it's really not about the simulation (wouldn't be bothered if it turned out current world is a simulation, although I'd like to go higher), not especially about separation, and only slightly about deception (certainly losing all impactfulness becomes more irreversible if the AI is lying).
Hmmmm..
My own view: -Separation is very, very bad. I'd be somewhat OK with reality becoming subjective but with some kind of interface between people but this whole scenario as stated is approaching the collapse civilization so we can't FOOM level. My personal reaction to seeing this described as better than status quo was somewhat similar to playing Mass Effect and listening to Reapers talk about 'salvation through destruction' and ascension in the form of perpetually genocidal robo-squids. I mean seriously? 'All your friends are actually p-zombies?' Are...
I offer this particular scenario because it seems conceivable that with no possible competition between people, it would be possible to avoid doing interpersonal utility comparison, which could make Mostly Friendly AI (MFAI) easier. I don't think this is likely or even worthy of serious consideration, but it might make some of the discussion questions easier to swallow.
1. Value is fragile. But is Eliezer right in thinking that if we get just one piece wrong the whole endeavor is worthless? (Edit: Thanks to Lukeprog for pointing out that this question completely misrepresents EY's position. Error deliberately preserved for educational purposes.)
2. Is the above scenario better or worse than the destruction of all earth-originating intelligence? (This is the same as question 1.)
3. Are there other values (besides affecting-the-real-world) that you would be willing to trade off?
4. Are there other values that, if we traded them off, might make MFAI much easier?
5. If the answers to 3 and 4 overlap, how do we decide which direction to pursue?