What would you do? The rest of your life spent on that island slowly going mad or try a daring escape in which there is a good chance you might be killed?
I guess the answer to that question depends a good deal on your age.
Didn't Devil's Island strike you as being a lot more mellow (dare I say it) and pleasant than the penal colony? It's like Papillon was rewarded for his five years in solitary.
I can understand Louis wanting to hang back their with his pigs, rather than take the big jump with the coconut raft.
I'm 23 so I will definitely do the leap of faith rather than staying alone with onlys animals and a garden seriously, I mean life doesn't deserve to be lived alone, without someone in your life I think you are nothing (just my opinion), add to that that not only you can't find a wife/husband on this island, but there is not a lot of things to do, and the neighborhood is mostly composed with criminals, with some of them stealing your food...I would probably stay if I was old enough (probably 60+) but if I was the age they are I would go without a doubt.
Also, I thought it was cruel for Louis cause the situation is more "ok" if you are with a friend. That's why they should have both jumped or both stayed ! After the film I thought "now Louis will spend the rest of his life alone with his pigs", I find confort by thinking he may socialise with his neighbors even if some of them are stealers.
I think after all they had been through, if I was them I would have stayed on the island. That kind of extreme hardship that Papillion went through, almost dying after spending years in the reclusion building ( I think it was called ), made the island look like paradise.
They had nice little houses and nice little areas for gardens, and the view was great. They weren't young men anymore and Papillion was gray-haired and worn-out physically from all the abuse and neglect he had taken over the years.
It wouldn't be a great life but it would be a half-decent one especially for well worn-out convicts.