"Most of my travel is in business class on business to North America and Europe (and points in between).
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If most of your travel is in business class , I would suggest going for the BA scheme unless you are planning to use AA for your transatlantic flights. They may or may not give you a complimentary status match, but that shouldn't be much of worry since you will have benefits by virtue of the class of travel. Getting BA silver the hard way will require attaining either 700 or 400 tier credits depending on where you register your membership. It will be 400 in continental Europe , 700 elsewhere. A flight in business class from Europe to east USA will get you 120 credits each way. A connecting flight in europe if you take one will get you 30. Any US domestic flights up to 2000 miles in 1st class will get you 45. To attain Gold ( OW Emerald ) you will need to attain 800 or 1700 points based on residency.

Dave