The Grand Canyon is not one trip but several, sold by different operators and run on different land. The South Rim is inside Grand Canyon National Park, open all year and reached from Flagstaff, Williams or Phoenix, or on a long day by bus from Las Vegas. The West Rim, with the Skywalk, is on Hualapai tribal land outside the national park, closer to Las Vegas and sold on its own tickets. Helicopter flights leave from Las Vegas, from the West Rim and from Tusayan, just outside the South Entrance, and the Grand Canyon Railway runs from Williams to the South Rim.
Which one is right depends on where you are staying, how long you have, and whether you want the national park itself or the closest canyon views to Las Vegas. These pages compare them plainly.