There are so many options to choose from that it is in fact easy to get confused. Briefly, there are daytime and night-time tours. You can fly over Las Vegas, or fly from Las Vegas to Grand Canyon.
Some of the tours are:
Voyage over Vegas - daytime tour over Las Vegas.
Vegas Nights - a tour similar to Voyage over Vegas, the only difference is it takes place when it is dark outside and you can enjoy the lights extravaganza.
Wind Dancer - a tour to Grand Canyon, with landing at Canyon.
Silver Cloud - air-only helicopter flight from Las Vegas to Grand Canyon, no landing at Grand Canyon.
Dream Catcher Sunset - a helicopter flight to Grand Canyon, with landing at Canyon, happens on sunset and allows seeing magnificent views not only of Grand Canyon, but a glittering Las Vegas Strip you will fly over on the way back.
Skywalk Odyssey - a flight to Grand Canyon where, after landing at Grand Canyon, you will be able to visit the famous Skywalk, expedited admission to Skywalk included.