Assuming Slammers holds onto DA rather than push it off on LAFC directly, I would bet....
1. Beach FC (has shown that they can develop playing a pretty form of possession in recent years)
2. Slammers FC (hopefully you understand the difference between Slammers FC and CDA Scammers FC. One is the genuine article and the other markets the name)
3. LA Galaxy (with 10 years of DA experience and a MLS parent team, has yet to demonstrate any ability to develop talent)
That is my take ONLY taking into account the 3 you mentioned. There are other players in the game but I assume you asked about the 3 you listed based on geographical reasons.