Originally Posted by
chgoeditor
(For example, American, which is my program of choice, gives you four upgrades for every 12,500 elite qualifying miles flown. Each of those upgrades is good for a 500-mile flight segment. Without even getting into the various EQM calculations, you first have to earn status before you'll get those upgrades, and then you'll probably have to fly in excess of 30 segments before you get four upgrades -- and you'll burn through those on four flights, then have to wait almost a year before earning your next batch.)
This is not correct; as LAX-SFO is only 337 miles, OP would be eligible for complimentary upgrades and doesn't need to earn or burn certs.
I wouldn't go out of my way to spend lots of extra money concentrating flying on one airline. But if I tried to concentrate, it would be on AA or DL. Here's why:
The biggest reason... AA has about as many frequencies as DL, and essentially flies exclusively E-175s, which are among the most comfortable seats in the skies, even in coach. DL flies a mixture of E-175s and 717s (though the 717s aren't awful with the 2-3 seating). United flies a lot of A320s and 737s, which I don't find comfortable.
Delta flights between LAX-SFO are operated with the Shuttle product, with 14 flights a day, so there are plenty of options. Free food and beverage, even if you're seated in Economy.
DL plays a lot of games when it comes to offering upgrades, even to Comfort+ seating. On the other hand, neither SFO or LAX is a hub for DL, which helps keep the elite population somewhat down. I found my ability to get Main Cabin Extra seating on AA even as a Gold was far better than being able to get Comfort+ on DL.
One-way flights between LAX-SFO currently run as low as 5,500 miles on DL (we've seen 4,500 in the past) if you can plan ahead at least 3 weeks. AA's minimum is 7,500, and UA's minimum is 10,000. DL also has better availability at their "saver" rates than AA has at theirs.
The only way lounge access is going to happen is if you buy a membership or pay for a credit card that gets you in. Totally not worth it until you're 21.
All that said... I would consider how often you really will be going home. I don't know anything about you or your family situation, and I certainly acknowledge there may be perfectly valid reasons you are forced to return home regularly... but more often I have seen parents still trying to hold on to their kids after they go to college, and likewise I've seen students cling to their home. Assuming you're attending a typical 4-year residential program, and have no such demands in SFO that require you to return home so often, I suggest jumping in with both feet. Those 4 years will go by in a blur... you'll have the time of your life and will form relationships that you'll carry with you forever. This becomes much harder to do if you're constantly bailing out to go home.