Chicago to London > same price, BA or AA??? Also, Do either of these airlines have the systemwide swu upgrades available like United. Thanks!

I don't understand why(in the cross-posted thread) people agreed BA should be chosen even you may not earn any miles. Anybody can give me the insight?

Haven't seen the cross-posted thread and probably won't, but for reasons discussed at length in the AA, BA and oneWorld forums, an AA flight between the U.S.and London won't earn BA credit and vice versa, even though all other flights on either airline can be credited to either under oneWorld agreements. So, if the OP wants credit in either AA's or BA's program, flying the other one on this route isn't an option. Period.

If that's not a factor, IMHO it depends on class of service, but overall I'd give BA a slight edge.

AA has system-wide upgrades much like United's. Top-tier members earn eight per year (ten this year if they fly an extra 25,000 miles and pick that option); four go to anyone who crosses a 2+ million-mile milestone, counting all earned, purchased, transfered or gifted miles from all sources; and four also go to 1MM (ditto) flyers who live outside North America. They're transferable, so if your cousin has a couple of spares and wants to do you a big favor, he/she can give you a couple.

Got your point.
But some of AA booking classes, such as Q does not earn miles between US and Europe. Don't know if BA's World Traveller Calss earns any(BA miles).

All BA revenue classes earn BA Miles, at varying rates depending on how discounted they are. The lowest booking classes earn at 25%, with nothing towards BA Executive Club status.

There are also joining qualifications for the BAEC. The way that the airline would like you to qualify is to have a booking for a status-earning booking class flight. But once you've joined, however you've qualified, you will earn miles for all flights whether or not they qualify to earn status.

More information in the Ultimate British Airways Guide.

If it is a level playing field on ff miles and the airport for the flight is the one you want to have, I'd go for BA even in the cheap seats. BA has the slightly more expensive WT+. AA does not.

The food on BA is better.

If ff miles matter to you and you are already a BAEC member, then you need to do a lot of pencil work to make your decision. The best value in flying may be the use of BA miles to upgrade.

If you want a wad on ff miles, make sure your ticket on AA will give you those and choose AA.

So here's my list: airport choice
ff miles, type and quantity
price

It appears that your question has been answered. As this doesn't appear to have anything to do with the "latest frequent flyer program buzz" I'm going to close it here.

Regards,

Flipside