I was down in October and rented with Dollar. Part of an Expedia package so can't really compare to daily rates.
There's a free shuttle from McCarran (in front of the terminal) to the huge car rental complex out on Gillespie, about 10 minutes away.
If you're mostly on the strip, I'd go with the Deuce (bus) but for anything else (Red Rocks, Hoover Dam) rent a car. Or helicopter.