My preference is to show the on-graph-paper maps to the players, but if they want to draw their own, they have to use plain paper. I have an old essay cum rant that touches on this:
Why Game Masters Should Give Players Exact Distances
The usual argument, in a rpg, against giving players exact distances is that one cannot simply tell, without some sort of tape-measure, that a pillar is 5'3" high, or that the distance between two walls is 21' While this is true, it is also largely irrelevant.
First, people can judge distances pretty well by eye. What they can't do well is put these distance judgements into feet and inches, or into other easily-communicable forms. I couldn't tell you, without measuring, how many inches it is to my computer monitor - but I know the distance well enough to reach out and touch the screen, without either falling short or attempting to put my hand through the screen. Likewise, I can toss a wad of paper into a wastebasket across the room: I know, intuitively, the horizontal distance, vertical distance, weight of the paperwad, and expected air-resistance, even if I can't put accurate numbers to any of these things.
Second, the difficulty of "translating" between intuitive distances and measured-number distances cuts both ways. When the intuitive side of the brain looks and says "yaa far", the numerical side is confused: "five feet? four? six? more? less?" But by the same token, when the numerical side of the brain is told "five feet", the intuitive side becomes confused: "huh? What does 'five' mean?" So being told "five feet" is not more precise or detailed than seeing a five-foot distance - it's fuzzy and vague in a different way, but it's just as fuzzy and vague.
Third, non-numeric descriptions of distances and sizes are often far more fuzzy than is commonly appreciated. For example, if a player asks "how far is the bridge above the surface of the water?" and the GM answers "pretty high", then the player might imagine an arch rising 25 feet above the water while the GM is thinking tall pilings rising seven feet above the water. Or vice versa. Or the player and GM might both think "tall pilings", while a second player thinks "high arch". The confusing and argument that can result from this sort of misunderstanding is not amusing, at least not to me.
Fourth, role-playing games suffer chronically from problems of information starvation and low bandwidth. The player's characters can constantly see and hear and smell and feel what the game-world is like, often with keen or even super-human senses, while the players are themselves limited to what the GM tells them. This tends to put the players in the position of the blind men and the elephant. To compensate, the GM needs to communicate well, even if this means giving information in a compressed, or stylized, or "too accurate" form. Even if the GM cleverly gets around the number-translation problem by saying that a railing is "this high" (holds hand above ground) the players only see the indicated distance for a few seconds, while the characters see the railing's height for many seconds or minutes - a difference of a hundred-fold or a thousand-fold.
Fifth, GMs are as vulnerable to fuzziness and distortion as players. When a GM gives an "impression" (or a white-board sketch) from his notes or a module, the result goes into the players' heads through two sets of perceptual distortions: The GMs and then the players. (The players' characters on the other hand, should have only one perceptual distortion to deal with - their own.) To misuse legal terminology, where the PCs should be witnesses to (e.g.) the Great Cavern of Ogg, they often up having only hearsay knowledge of it, in spite of being "there".
Sixth, accuracy is not precision. I'm not calling for GMs to give distances precise to the inch (unless the distance is only a handful of inches total) but for GMs to give accurate distances with a precision within 10%. This means that distances of over 5 feet be given to the nearest foot, distances of 25+ feet be given to the nearest 5-foot increment, distances of 250+ feet be given to the nearest 25 feet, and so on. "About [number] feet" is short and sweet.
Finally, I do realize that players can abuse exact distances given by the GM. However, I think it better to deal with or live with these abuses rather than to suffer the problems of the GM not giving exact distances in the first place. And these problems can be dealt with. For example, I suggested in a long-ago /Dragon/ article that players be given exact distances in dungeons, and allowed to draw maps even if their characters weren't mapping - but that the players be required to draw the maps freehand on plain paper (i.e. no graph paper and no rulers). Not only would this give about the right degree of "fuzziness", it would also produce maps resembling those that the characters would have "really" produced, either then or later. After all, who ever heard of an antique treasure map drawn on graph paper?