I think their meanings are really close, brenobrendan. If you tell me that the room has a panoramic view, I know that you have a wide view of some scenery.
If you tell me that your room overlooks the valley, I assume that you have a wide, full view of the valley. I suppose it is possible to have a restricted or narrow view from this room, but that doesn't seem likely.
Without forming any opinions about hotel room views...the meanings of the two terms are not the same.
"Overlooks the valley" says you can "look down into the valley". You might take lovely photos with your camera.
A "panoramic view" is an exceptionally wide view. Special cameras are need to take a picture of a "panoramic view". They actually take several normal pictures, and later merge them together using "image stitching" technology. Wikipedia has an article on "panorama".