Personal opinion, I'd drive. I commuted out of Burbank to Vegas for about a year a few years back before LA base. SNA has a few less SWA flights but a couple delta so about same total. If you are an AM'er you'll have to fly to Vegas the night before and stay in a hotel or crashpad, no flights get you there early enough for almost any trip. If you're a PM'er you're usually not going to make the last flight back to SNA after your trip, so again hotel or crashpad for the night or I guess lounge chair if you can stomach it. While you're on reserve, which could be a while with this slowdown, you're flying to Vegas to sit around, again night before for an AM and probably not getting released in time to go home on a PM. Hotels in Vegas are plentiful and not that expensive if you plan in advance but if big shows are in town it can get tough to find something last minute reasonable.

Haven't really looked at LA lines but if they're like most other bases on an AM you're probably showing before most traffic, 5AM or so and getting done midday so home before worst of afternoon traffic. On a PM you'll show midday and get done after 10PM. Unfortunately with our 2 hour call out for reserve you may end up having to preposition yourself a bit closer to LAX but having done similar in another base I'll take watching a movie or hanging out drinking coffee an hour from home over flying to Vegas to sit around the airport.