I gotta spread some xp around.
I do find it interesting that "meaningful choice" is linked with "appropriate challenge" which in turn is translated into "beat the snot out of it in a standard fight" these days.
I don't quite agree with that. Nor do I agree with the chess comparison.
not picking the best move in chess is a failure in the player. It's not just a choice (ex. I could do this really smart thing, or this really dumb thing) it is failing to see the best move.
Now jester makes a good counter that some players DO choose to go to the really harder levels. That to me is a good enough argument that there is still a Choice in whether to go deeper. Though this might also be an example of "Retreat Forward!" tactics.
Back to EW's point, I think there's gotta be a middle ground solution to the difficulty of encounter problem. Even if we accept my original position that "going deeper is dumb, therefore not a Choice" it is equally unrealistic that every critter in the area just happens to be level appropriate.
In actuality, I don't have a problem with "going deeper is dumb" being a Choice. The player has intel to make a decision (maybe to shake off a patrol that seems too tough for them). What I tend to dislike is the player having no intel and ending up in the lair of the 20th level bad guy when he's first level. With no foreshadowing/clue that this was not a safe place to be. The player didn't really get a choice, if all he knows is "there's a door, do you open it?"
I tend to look at the game progression as the starting region is small with small threats, and as the party rises in level, their region of awareness grows thus they face bigger threats, or the bigger threats move in due to the loss of bottom feeders and the draw of the PCs being 'bigger fish".
I like some variety in strength levels of opponents, so not everything is 'PC level", but in the same vein, I don't tend to put the mega-powers who hate the PCs right next door to them.
Anyway, this has less to do with plots in sandboxes. What was Lost Soul's question?