Originally Posted by Tyrolean

I would go for QF.

If you fly business-class you will get status very soon.
(You get 40 TPs on flights under 600 miles and 60 TPs on flights over 600 miles). (not only the flat 40TPs of BA in Business).

All fare-classes get Tier-points (even the deepest discounted classes).

All fare-classes on IB earn 100% miles.

No worry about transatlantic flights on AA/BA that do not count.

QF has a lifetime status (long way, but possible).

If you need lounge-access on QF/BA/AA you can buy a Qantas-Club membership.

Earing rates are as bad as with BA, but you get more miles.

Be aware: QF-Silver doesnt get you into the lounges, you need gold for that, but that gives you 50% Bonus on QF/BA/AA.

If you fly Business-Class you get lounge-access anyway