The Great Plains are located to the east of Las Vegas, Nevada. The terrain is very much flat with slight slopes and dunes. To the west of the Great Plains are the Rocky Mountains. Las Vegas on the otherhand is surrounded by mountains with the Spring Mountains to its left. This is a picture of the Spring Mountains.
Also, the Great Plains weather varies in the sense that it is always changing and very unpredictable. Regions close in proximity can experience a difference in weather at the same time. Whereas in Las Vegas, many can experience sunshine throughout the year. So sunscreen is a must anytime you travel to Las Vegas.
Sources:
http://www.lasvegas.com/listing/spring-mountains-national-recreation-area/1499/
http://blogs.involutiondigital.com/blog/bid/249894/Top-10-Stupidest-Things-Tourist-do-in-Las-Vegas