salt, BA is cheaper than AA on certain routes. SFO-BOM/DEL/MAA is only 100,000 miles in Biz RT on BA while it is much more on AA (I believe it is 150,000 miles). On the other hand there are a lot more routes on which AA is much cheaper. The 3 airline OW award allows similar awards using both AA and BA.

On the whole I do recommend AA plat and AA miles but the recommendation may be different if the flying patterns are different.