You lose the AA upgrade if you remove the AA number from the booking -- there is no way around that. The only real value of other OW status is the AC/FL access for domestic US flights. Otherwise EXP is still worth more for opups than BA Silver (know that for a fact -- despite all the hints that BA takes care of its own BAEC members first, it just isn't true, they follow the OW status). If you fly F/J fares then QF Emerald status is the easiest to obtain, also a few of QF's routes are ones where QF status comes in useful. BA has less of those routes and generally more flights, so BA Gold is less useful than QF Platinum. But AAdvantage is generally the highest yielding program to use, in terms of value for miles earned, so switching to a 2nd program is strictly for special purposes. I think Asiamiles are the most valuable of the programs (but also earn the fewest miles, as CX has smaller status bonuses). Overall CX Diamond is absolutely the most valuable Emerald, but the biggest value is if you fly CX a lot in non-premium classes. I'm happy with QF despite their problems and recent devaluation, but I credit much of my flying to EXP (now if only they had a double or triple EXP status).