I used to fly JFK-LGB a lot on B6, then moved to flying JFK-SAN when B6 pulled out of LGB. I hate LAX too and would rather do the longer drive to SAN from Laguna. I am starting to shift my travel now to JFK-SNA on AA. I don't think either program is going to get you a lot when you are booking an economy ticket (you are not generating significant revenue when a one-way fare is probably around $200). Mosaic will get you early boarding, separate Mosaic luggage check in area, and that is about it. Upgrades to Mint are not available. On AA, you will probably be gold which will prevent you from getting upgrades to first/business since many people will have higher status.