The geography decides it
Nevada has two useful airports. Harry Reid International (LAS) in Las Vegas is the eighth-busiest in the US and serves the Strip, Boulder City, Mesquite, Laughlin, and southern Utah/Arizona routes. Reno-Tahoe International (RNO) is small but well-connected on Southwest, United, Delta, American, and Alaska, and serves Reno, Carson City, Lake Tahoe, Virginia City, and the whole northern half of the state.
If your destination is Lake Tahoe south shore, RNO is 55 minutes. From LAS it's 7.5 hours through the desert. If your destination is Great Basin National Park, RNO is 4.5 hours and LAS is 4.5 hours (via US-93). If you’re combining Vegas and Tahoe, fly into one and out the other; the one-way rental car fee is usually cheaper than a spare day of driving.
Cost, connections, and hassle
LAS has more nonstops than any airport in the Mountain West: direct from every major US city plus 20+ international routes (London, Frankfurt, Seoul, Tokyo, Mexico City). RNO is regional; you’ll usually connect through San Francisco, Denver, Seattle, LA, or Phoenix from farther away. Fares to RNO run $80-150 more than LAS from the East Coast because of that connection.
Ground time matters too. LAS to Strip is 15-25 minutes and $18-25 by rideshare. RNO to downtown Reno is 10 minutes and $12. RNO to South Lake Tahoe is 60-75 minutes and there's a shared shuttle (South Tahoe Airporter) for $35 per person, or rent a car. In winter, the Mt Rose Highway to Incline Village can close in a storm; check conditions before you commit to a rental instead of a shuttle.
Good to know
Can I fly into Vegas and take a bus to Reno?+
You can (Greyhound and FlixBus run it) but it's 11-13 hours. Just book a $60 Southwest hop between LAS and RNO instead; it's under 90 minutes.
Which airport has better lounges?+
LAS, by a mile. Multiple Priority Pass options, a Centurion Lounge, Delta Sky Clubs, and United Clubs. RNO has one small Escape Lounge in the B concourse.