Terminal 1 gets 3 stars and Terminal 3 get 5 stars.
Terminal 1 is a decent airport plagued by drab and dated interior. The carpeted floors, odd smell, and terrible food options make it a mess. The slot machines and the obnoxious "Vegas" decor gives the airport a unique style which I kinda dig.
Anyway, going through security isn't too bad. The employees do their jobs and most are really friendly. When my boarding pass didn't indicate my gate number, I asked a security guy for help and he pressed some buttons on his phone and within minutes he got the number.
Parking here is okay. It's easy to navigate and use. Pick-up and drop-off areas can be hell, but that's always expected.
The new and gorgeous Terminal 3 is the clear favorite. Modern and it smells great; the terminal upgrades McCarran's reputation. Once you get passed security, you're rewarded with slots (if that's your thing), shopping, and decent dining. I just wished there were more outlet plugs to charge your electronics. Oh well, it beats nasty-ass Laguardia to a pulp.