Of course the one-boxers get more money: They were put in a situation in which they could either get $1 000 000 or $1 001 000, whereas the two-boxers were put in a situation in which they could get $0 or $1000.
When faced with this decision, you are either in the real world, in which case you can get an extra $1000 by two boxing, or you are in a simulation, in which case you can arrange so your self in the real world gets and extra $1,000,000 by one boxing. Given that you can’t tell which of these is the case, and that you are deterministic, you will make the same decision in both situations. So your choice is to either one box and gain $1,000,000 or two box and gain $1000. If you like having more money, it seems clear which of those choices is more rational.
When faced with this decision, you are either in the real world, in which case you can get an extra $1000 by two boxing, or you are in a simulation, in which case you can arrange so your self in the real world gets and extra $1,000,000 by one boxing. Given that you can’t tell which of these is the case, and that you are deterministic, you will make the same decision in both situations. So your choice is to either one box and gain $1,000,000 or two box and gain $1000. If you like having more money, it seems clear which of those choices is more rational.