Which effect is stronger can depend of whether the rules cover the desired action with an interesting mechanic, whether the DM planned for diversions (through world building, lists of things that can be injected in to get things back on a track), and how good at improvisation the DM is.

Agreed, though again, the rules are a secondary problem at best. Almost every game has catch-all rules that can be applied to any situation, even D&D. For example, if my players wanted to plow the field successfully, I'd have them roll "Knowledge: Nature" or, if they don't have it, "Knowledge: Local". If they just want to fix the plow, it'd be a "Craft" check... etc. The problem is not with the rules, but with the plot and the setting. As the GM, I probably have a detailed map of the Drow caves and an org chart of their social structure; but I know squat about growing wheat. I could find out on Wikipedia, of course, but taking the time to do so would break the flow of the game.