There is more than one way to hold a lottery among our castaways. You could get five ping-pong balls, label each with the name of a different castaway, choose one ball at random, and designate that ball’s owner the winner. Alternatively, you might proceed as before but keep drawing ping-pong balls until you’ve taken them all; whichever name you draw last, call her the winner. You could also assign each castaway a sector on a wheel of fortune, spin the wheel, and call whosever sector comes up the winner. And here is one more: those castaways who have landed on the island with more people, call them the winners. [...] [W]e cannot help but see each person as coming to his or her island by chance because we know nothing about them. And this means that we can think of these island assignments as made by a lottery—by what I call God’s Lottery—and declare those who landed on Isle de Trois are the winners of that lottery.
Again, it seems to me that the only available distinguishing feature is counterfactual openness, but it seems very dubious to think that that could make a moral difference. So we should not think that there are any special reasons of "fairness" that count against simply saving the greatest number.
* (Thanks to Govind for the pointer)