That leads nicely to the next question - the interests of the snake. It's worth starting off this side of the discussion by pointing out that most adult snakes (this seems to hold for box turtles too, and probably lots of other land critters) released far from home generally do not survive. We tend to think of reptiles as stupid creatures reacting to their landscape on a moment-to-moment basis, but they probably have a much more refined sense of place and landscape than we usually give them credit for. I'll wager an adult ratsnake knows every greenbriar thicket, stumphole, and hollow tree in its territory, a territory that could cover a few square kilometers. When you release a snake that has lived its whole life in a specific place in another place, it starts looking for home. It might set off over hill and dale looking for that home, and it might get run over by a car or picked off by a hawk while it's wandering. It might spend too little time hunting and eating while it is searching, and winter might find it too thin to make it to spring. It would be kind of like dropping me in downtown Moscow. I don't know the language, I don't know anyone I could crash with, I don't know which are the sketchy neighborhoods I should avoid.
The result is that relocating adult snakes tends to go badly. There are exceptions, but the point is that relocating a snake more than a mile or two from where you've found it generally is the same as killing it. It just takes longer. This does not hold as true for baby snakes. They might face slimmer odds for a variety of other reasons, but they tend to be better able to settle down in a new place, perhaps because it is natural for baby snakes to wander around until they find a nice spot anyhow.
Of course baby snakes generally don't survive in the wild. Let's assume that an adult female ratsnake breeds for five seasons before she gets picked off by a hawk or run over by a car, and if we assume she averages 6 hatching eggs per year (both round estimates for the sake of argument: she might breed one year or fifteen before her demise; they generally lay bigger clutches than that, but I'll assume some years they get eaten by skunks). In a stable population an average of only two of any reproducing female's offspring will make it to maturity. Two divided by thirty gives us pretty crappy odds. I might be tempted into thinking I'm giving the snake a life of glorious freedom, wandering forests and thickets, raiding nests and basking on old tree branches, but the options are more realistically either a long and well-fed life in a boring box versus a few months of nervous freedom ended by the snip of a crow's beak.
Like I said, I've got a couple weeks to make the decision, so let me know what you think.