I'm frequently surprised by how many areas (outside CA) are still using coach pitch - or even machine pitch - at the 10U level. IMO, this delays the development of players on both sides of the ball, and could be a contributing factor to why there is a trend towards a higher talent level in CA. From my own observations, even 8U players are capable at executing at a pretty high level.
I can't say definitively which way is better, but we are taking a look at this for our rec league. We play SF peninsula and south bay teams for summer and fall ball. It's not SoCal, but there is good softball. Our league has player pitch at 10U but we are reconsidering after learning that some of the better programs in fact have coach pitch at 10U.
Awesome pitchers will still be awesome. The coach won't get in much when they are throwing. But on the other side of the equation, it greatly multiplies the hitting and defensive action that occurs in a game to have coach pitch instead of walks. I could also see an argument that it could help pitchers as well. Instead of pulling a borderline pitcher due to some walks, coaches may instead be able to let them stay in games longer, and learn how to tune in their control in a game situation without fear of being yanked so soon.
For our 8U division, our league uses a hybrid player-coach pitch format. It's player pitch until ball 4, then the coach pitches for however many strikes are are left in the count. For example, if the coach takes over on a 1-strike count, her/she gets 2 pitches to the batter to either put the ball in play or strike out. There are no walks. About halfway through the Spring season, we change to all player-pitch to get ready for the league tournament and All-Stars. This has been successful for us in developing both pitchers and hitters. Our one 8U All-Star team had two girls who could throw 40+mph from 30', and very rarely gave up more than 2 or 3 walks in an entire game. This level of pitching was not uncommon in the All-Star teams we faced. At the State Champ tournament, our pitchers were average.
I agree that awesome pitchers will be awesome pitchers, but I believe they need circle time in game situations as part of their development. Similarly, the betters batters need to face pitchers who are trying to get them out to hone their skills. Coach pitching is great for building confidence and getting some success for the lesser-skilled kids.
Yes we are currently using the exact same rules as your league. Hybrid, then girl pitch only. Sorry, I may have misled, it never occurred to me a league would do coach pitch only at 10u.
The nature of SoCal communities comes into play too, it's one huge suburban sprawl, so weather+population+space.Most other areas have true cities so the population gets dense where the land gets scarce.
In NorCal, sprawling areas like SJ, Sacto, Stockton, have power org's, while SF does not.