CSL vs. Cabo Pulmo or even vs. La Paz (for the sea Lions at Los Islotes) is really a matter of what you wish to see and how many days you wish to set aside for it.
Do I find the diving in CSL interesting? Not anymore - but that is me. With a lot of luck, something really interesting might swim by - mobula rays, cownose rays, maybe even a whale or a whaleshark at the local and Corridor dives, or hammerheads at Gordo Banks. There is a small sea lion colony at Land's End (local dive), but they are not very playful. So for me, not really anything "exciting" for which there is a reasonable chance to see besides fish, eels and bottom-dwelling rays.........as opposed to CP (the bulls at El Vencedor and arguably the largest school of big eye jacks anywhere) or La Paz (the sea lions there are a lot more interactive, especially the juveniles, and there are years when the whole place is shrouded in sardines).
With that said, if you've never dived out of CSL, it might be worth your while: the dives there are categorized as Local dives, Corridor, and Gordo Banks, in ascending order of cost. And from a logistics standpoint, it is by far the easiest for your situation because there isn't the lodging and the transportation that you need to arrange, whether by car rental (see note below) or private shuttle - to get to the other places and back. And when you are done, you are ready to board your liveaboard without the hassle of traveling back to CSL.
I fully agree with FettSolo in that if you want to do Cabo Pulmo - and that timeframe is very good, water conditions and viz-wise - you need to stay there for a few days to have a chance to do the choicest sites. Doing the day trips out of CSL to CP puts you close to the bottom of the totem pole when it comes to CP divesite selection.
I've never been to the Red Sea - I've always wanted to, but never garnered the courage to travel there carrying my American passport. Probably unfounded phobia, but.... But I have read enough and seen enough pictures and videos on the Red Sea to think that to compare it with Socorro is too much of an apples to orange comparison. Shooting from the hip, I'd do them both - and not just once. But if I had to choose one or the other, it'd still boil down to what I'd like to see.