I suppose one argument could be that a detailed map can provide supplies/gear for specific areas, whereas a simple map would not. For example, a simple map of the Territories could be considiered insufficient to provide a supply/gear bonus for a specific area, say, the shoreline around/near Grasslake (or a particular settlement/city, or the scent border, etc.).
You say you’re trying to make a map. The GM sets the obstacle. Therefore, if you’re trying to make a map of Barkstone for an invasion, he says it’s a complex map. If you’re drawing a map to your hideout or treasure, it’s probably a simple map.
Ah, that’s different that I was thinking of it. So, a player would say “I want a map to help me get safely from Sprucetuck to Port Sumac” and the GM would make a judgement call that this would require an Accurate map (one that shows all the twists and turns of the trail and important landmarks along the way) rather than a Detailed map that might be used for planning an invasion (only showing elements of strategic significance) or a Simple map that could be used to teach young mice the major cities in the Territories (on par with the map provided with the book).
Iota, I think your three examples are pretty good, but I agree with Luke, too. (go fig…)
I’d think the map to your hideout/treasure is probably a simple map because you’re going to be relying mostly on your own recollection to get back there, using the map as a rough guide. After all, you don’t want someone who stumbles across that map to have an easy time getting your goodies. I think your three examples are pretty good though. Now a map you plan to give to someone else so they can get to your hideout might be an Accurate map, and one so they can get in and out safely, avoiding the traps, would probably have to be Detailed.
As for the initial question, to provide the bonus, the map has to be appropriate to the task, just like any other tool. (You probably wouldn’t get a bonus to a challenge where you need to dig a latrine if your tool is an apiary smoker. A simple map of a large area probably won’t show enough detail to help you find a hidden cache of supplies, but an Accurate or Detailed one of a smaller area probably would.