The Nature of Consciousness
I probably should've been more clear. I'm not talking about differences in whether something like tomatoes actually exist in one but not the other. I'm talking about intrinsic differences that arise from following the rules of a world (physical laws) like whether tomatoes COULD exist in one but not the other.
In the case of tomatoes, if the two worlds had the same physical laws and one of them had the possibility of producing a tomato, you would point out how a biochemical configuration representing a tomato can exist in the other world as well. You would not be able to say that there are two worlds - each which have the same physical laws in which tomatoes can exist in one but not the other. Either they can exist in both or they can't exist in both. It would be a logical fallacy to say otherwise.
In the case of consciousness, you can imagine two worlds - one in which consciousness exists and another where it doesn't despite the two having the same physical laws as evident by the philosophical zombie introduced by "I like Sushi." Since the zombie acts and reacts in the exact same way a real conscious person would, it would still follow the causality intrinsic in physical laws.
In logical proof, it's known that under a set of givens, if you hypothesize something and you have logical derivation that shows that you can evaluate something to be true and false at the same time, the thing that you have hypothesized is false. The negation of that is also true in that if you hypothesize something and you can't have logical derivation that shows you can evaluate something to be true and false at the same time, the thing that you have hypothesized is true.
The fact that you can imagine something and not find any contradiction in its imagination shows that you don't have logical derivation that shows you can evaluate something to be true and false at the same time. This would make the hypothesis (consciousness not being physical) true.