You’ve been kidnapped and given a choice: would you rather be stranded on an island, dropped into an unknown forest, or locked in a strange building?
You haven’t said if the island is inhabited by natives. I might be scared of natives, especially if they were the people-eating sort. There are also lots of bugs and probably dangerous aquatic animals, like crocodiles and alligators, lizards and snakes. Gives me the shivers already!
Now the forest, depending on the location and the climate, might be slightly more appealing. Plenty of wood for fires and building a shelter, but still the issue with animals and snakes, though I think there are fewer deadly snakes in forests. Bears would probably be the biggest concern. If it were an Amazon rain forest, all bets would be off.
A strange building sounds the most secure and sheltered from the elements. But what would I eat? Mice and bugs? Yuk. I need a better description of the building. and whether or not it at least has running water. It was my first choice until I thought of sustenance. Again, depending on the building, there may be no natural light; that could get pretty depressing.
Of the three dubious choices, I would have to choose the island. It would have the best climate, presumably, more food including healthy fish, though drinking water might be a problem, however, there might be a choice of plants to provide hydration. One would learn about the snakes and critters, where they live, and how to avoid them. Snakes could also be eaten, there would be fuel for fires, and certain plenty of building materials. Few tribes still exist that are man-eaters, so if there were natives, I would probably have a good chance of making friends with them, even help them as they might help me.
If escape is part of the equation, then the building would be my first choice, the forest second (unless it’s in the Amazon). Forests usually connect with habitation of some kind, and other people may come into the forest to hunt, trap, or just enjoy the surroundings. An island would present far fewer options for escape, and I’d really have to know where I was before even considering trying to escape.
To be truthful, I’d prefer to stay home, if you don’t mind. Send someone else.