To the OP;
I commute LAX to LAS as a middle of the road FO. Out of training, I got ACY for 1 month and DTW for 1 month, then got LAS as a base. This changes month by month so your mileage may vary.

It took about 9 months from date of hire to get a line. Reserve wasn't too bad compared to my regional airline. If there was something they were going to call you for, it was generally on your schedule 24 hours in advance (which is something nice most other airlines will not do). If you are trying to be cost-effective, you will need a crashpad while commuting on reserve. Once you have a line, it isn't necessary if you'd rather do hotels. I fly with a handful of commuter captains who still keep crashpads. The comfort of knowing you have a bed to sleep in regardless of what happens with your commute can be nice.

LAX to LAS is considered an easy commute and a lot of guys here (and at delta, united, virgin, ect) do it. I use the word 'easy' based on the frequency of flights per day and the fact that it is mostly mainline with two jumpseats that operate the flights. With that being said, as mentioned above, any commute is very undesirable and adds a lot of unnecessary displeasure and stress to this job. Some deal with it better than others and you will hear different opinions on how 'bad' XXX commute is.

With all that being said, to ultimately answer your original question, even as a commuter once you hold a line in LAS you can expect a decent schedule and plenty of time at home compared to your 91/135 job. Very quickly you will find that the commute will chip away at the time you will be able to be home and there will be plenty of nights you get delayed on the last day of your trip and you will be stuck in Vegas. As someone who has both lived in based, commuted and is a SoCal cheerleader; I plan to move to Vegas in the near future.