It has been my experience over a lot of D&D play that fun always improves when you give the players the map. Giving the players a map of the dungeon means that they can plan ahead, that they can make meaningful decisions about where they're going and moves one more thing from the "DM hassle" basket to the "players can keep track of it" basket.
Now, that's not saying that you should show the whole map to the players if the characters wouldn't have access to it. It's just saying you should find reasons for the PCs to get maps of the dungeon. Using History in a library to come across architectural plans of the old castle, perhaps, or finding a deceased previous explorer with a partial map, say.
And in giving the PCs the map, it doesn't need to be complete nor does it need to be accurate. A GM could create interesting surprises by having the map and the territory not sync up. (Though if they did this too often, no players would trust maps in their games.)