This makes me think that UA should be "out" as an option, because even at top tier, there won't be an upgrade chance without RPUs. With DL and American, there's an upgrade chance (albeit only at Executive Platinum with AA). The other plus of focusing on AA and DL is that they have a lot of routes from LGA (and JFK), whereas UA does not, so if you need to fly to other destinations at some point, AA and DL will be convenient.
Based on upgrades (again, not sure what the OP is seeking), I'd aim to reach 100K miles with AA (to reach Exec Plat) and 125K with Delta (to reach Diamond, which also gets lounge access, if I recall correctly). You should end up flying enough to reach top tier on each of those airlines. After you hit the 50K level on either airline, you might be able to status match to a *A carrier like TK so that you can at least have lounge access if you ever need to fly UA (or US to other locations).
Originally Posted by
amolkold
DL SWUs are a pain internationally, less so domestically (only need K+ fare).
For JFK-LAX, upgrades will be tough anywhere. AA only gives UGs to 100K flyers and makes lower tiers apply with 5 upgrade stickers. UA requires RPUs (regional SWUs) for JFK-LAX. Delta includes JFK-LAX on complimentary upgrades but with a 16-person cabin, usually no one below Diamond/Platinum will get upgraded during business hours. However, a SWU puts you at the top of the list.
DL runs 757s with Business Elite and some Economy Comfort. UA is changing to 2-cabin 757s with Business First and some E+. Right now, AA doesn't have a "Economy Plus" product on their 767s, but should when they start their A321s in the future.