Here is a map of Massanutten showing the different units: http://www.massresort.com/unit-maps.html
My favorite of the Summits is Summit Peak, get as far up as you can, they are usually helpful at check in to give you what you request. These have a nice view through the gap in the mountain and you can see down in the valley. I think these are Friday check in only but not sure. My least favorite is Hillside as these are the oldest and smallest. These two are north of the slopes, the others are south of the slopes and are all pretty much the same with some having views of the ski slopes. Again ask at check in for the best view. Also try to get an upper unit as these are a little bigger with a full kitchen, lowers do not have an oven. Uppers also have a cathedral ceiling (except for Peak) and fewer steps as you go down from street level to get to the lower units.
If you are going to ski, March will have poor ski conditions if the slopes are still open.