Originally Posted by
doctor15
On either airline you are unlikely to be upgraded as a Gold/Premier flyer, but you would probably have higher chances on AA.
You'd have to buy "stickers" for the upgrade on AA, right?
UA will give you the upgrade for free but you'll probably almost never get it.
On AA, you'd have to pay, but have a higher chance of success.
Until you reach some sort of elite status, tho, either one is going to be pretty grim.
AA offers (paid) challenges to reach elite. You could (just barely) qualify for platinum via challenge if you travel round trip every week in discounted coach. The challenge is $240 for platinum. Details
here.
Once you're elite, you earn 4 upgrade "stickers" every 10k miles you fly. Each sticker can be converted into 500 miles of space-available upgrade, so BOS-ORD is two stickers. In other words, about every sixth trip would have a chance of upgrade.
If you are short (in stature), I'd probably go for AA. If you challenge, you'll get to a higher elite status much more quickly (AA Plat vs. UA Premier). You'll be fighting for exit row seats rather than nearly-guaranteed Economy Plus, but you'll be earning far more award miles due to the Plat bonus.