I live in SEA and commuted to LAX for a few months back in 2017. It was, without a doubt, the easiest commute I've ever had as far as the sheer number of flights to choose from. Downside was expensive hotels. I was on RSV back then and I'd fly down in the morning for my sc shift and then just fly back home when it was over....and would do that multiple days in a row in order to avoid the stupid hotel costs (but if you do need one, Priceline seemed to give the best prices).

Someone else mentioned the volume of commuters between SEA and LAX and that is absolutely true. AA, the Eskimo, a half dozen regionals....there's always a jumpseater between the two cities, that's for sure. That said, remember the eskimo has 2 jumpseats on their 737s. Miserable? Yes. But it's a short flt.

All this aside, if god forbid I get displaced out of SEA in the future, I'd head for SLC. Pretty much just us and skywest pilots for that commute....rare to have someone physically occupying the jumpseat on that leg (at least that was the case when I was on the 73). Hotels are mucho cheaper in SLC, too. All other things being equal (ie, if there aren't trips that you prefer being flown out of one base and not the other) I really think it would be cheaper and less stressful to commute to SLC. Good luck whatever you try. With the current surplus on the ER up here, SEA is quickly becoming a difficult base to hold.