Hi, we have done both. With standard view, you will have a view of the valet parking/entrance to the Boardwalk, a lake with a fountain or if you have the longest walk to the end of the hall you could overlook the parking lot, tennis courts and the Tower of Terror at MGM in the distance. A lot of the standard view rooms on higher floors have illuminations views too.
For prefered view there are some rooms with views of Cresent Lake and the Boardwalk entertainment area. There are views of the main pool and of the quiet pool all of which can also see the canal that the boats use to get to MGM. Some of these rooms will also be able to see the Swan/Dolphin or MGM. The last section will have views of a red building (a maintance buiding I think???), the canal and the Swan/Dolphin. Many people have complained that this last section have the worst of the prefered views, which I agree with!
To help you with your decsion, if you like to people watch, the prefered views are more entertaining (pools or Boardwalk), but if you like quiet, the standard views are not going to have people milling around under your room. When we take guests we typically book prefered view. When it is just us, we typically book standard view! Hope this helped you some!