I had this dilemna both last year and this, chosing between BA and AA. I've settled on AA for this year; award levels are lower on AA and bonuses are better. I give up being able to book award flight on BA across the Atlantic.

If I were you, I'd definitely go for top tier in one of the programs rather than mid tier in both. In chosing between them, look at a couple awards you might want to redeem. What is the mileage requirement from each program? Also, look at a couple flights and calculate how many miles you earn in each program for that flight. AA is generous with its 100% bonus for EXPs, irrespective of cabin. Which airline is easier for you to deal with in order to redeem awards? Is there a home court advantage for QF? In my case, I find AA very easy; I just cashed in miles for a LAN trip in F to Peru.

If you earn excess vips, you can trade in Coupon Connection for awards of greater value. For example, it would be much more direct to take your kids via SYD on UA, wouldn't it? You can likely trade AA upgrades for UA SWUs in Coupon Connection. Or you can trade VIPs for hotel stays.