One thing to keep in mind is the lower earning rates for premium cabins that you get on Aeroplan (usually 125% of distance flown for C, 150% for F) vs. either M&M (200% in C, 300% in F) or bmi (same as LH on many carriers, but some exceptions).

Also, there is a difference on how many miles you earn on SQ Business Class flights between bmi (150% of distance flown) and M&M (200% of distance flown). However, the lower *G qualification threshhold and the more attractive redemption rates (especially when using cash&miles) still tilt the balance to bmi in my book.

Bottom line - if you see your self earning at least 100K miles in one year, every other year, go with LH. Otherwise, BD might be a better bet.

Oh, and if you do go the bmi route, make sure you get a status match to BD*G off your BA Gold. Details on how to do this can be found in the bmi forum (http://www.flyertalk.com/forum/forumdisplay.php?f=486 )