The earlier Lunar Orbiters didn't cover the polar regions. Clementine did but the resolution wasn't very good. LRO will take much higher resolution images and gather better terrain elevation data of the lunar surface including the poles. It'll be much easier to gather really high resolution images of the moon than of Mars or even the Earth because you can get a lot closer to the surface (<10 miles if you wish). As an added benefit, you can get some really high data rates from the moon because it's a lot closer than Mars, making it possible to return tremendous amounts of data. As always, there's a tradeoff between resolution and area covered for a given data rate. You might want to start at an orbit high enough to get good area coverage at a resolution of 10 meters or so, then zoom in on the particular points of interest for higher resolution. It wouldn't be hard to get better and 1 meter resolution (and perhaps much better than that) of specific targets of interest.