On the Boys side, the interesting thing is that the clubs that have probably supplied the most players to the LA Galaxy and LAFC academies in recent years, as well as a fair number of other clubs playing in the MLS Next league, would still be in CSL, making its Premier division pretty strong (and perhaps the second strongest division in boys socal in a couple of age groups, ahead of everyone but MLS Next). The big one is TFA and some of its affiliates, and there are a few others like Riverside City FC, but there are a ton of smaller clubs like Laguna Academy, Paramount, Orange County United, Puma USA Kickers, that tend to just be vehicles for individual super teams coached by a parent who knows the kids from the neighborhoods - and these are neighborhoods that are full of kids who live and breathe soccer - and gets them out there. These aren't clubs with big technical directors or directors of coaching who are trying to make a living doing this and therefore the attraction of SCDSL isn't as great. They often just have a couple of teams at their kids' age groups that affiliate with a club to meet CSL requirements like Kickers does with Puma USA or many teams do with TFA's affiliates.
That could change. AC Brea has had a younger team that was very strong and Boca OC has had some individual teams like this, but clubs like FC Golden State have long since hollowed out their core program with so many teams in ECNL, ECRL etc. CSL will still have a lock on a lot of boys talent in central LA and other areas north and east at the moment, if for no other reason than geography.