Originally Posted by
tjcxx
To keep BA Silver will take 15 transatlantic trips in Y. To keep AA Plat with the same 15 trips means a fare about £525 each. (according to my own calculator, I hope I've got it right)
So if your fares are £525 or more, AA would be better. You didn't say where in the U.S. you fly to.
Also I'm assuming you are U.K. based. The AA programme is now heavily biased towards credit card spend, and there is no credit card available in U.K., so I personally would go with BA because the balance swings sharply BA's way if you can run to W tickets when they are not much more expensive than Y.
Sorry I got this quite badly wrong with the AA calculation. My calculator was still using the pandemic reduced thresholds. The breakeven fare is actually over £700.
Just for completeness, crediting BA-coded flights to AA advantage would need over 20 trips to NYC, or over 16 trips to LAX. (at whatever price you find). The AA-coded flights calculation of £700 as above is destination mileage-independent.
Now if you are paying £700 and are credting to BAEC, then you'll probably be in a fare class that gives 35TPs per sector, meaning it will take only 9 trips. Sorry it's so complicated....
I can't really now see any reason why you would not credit to BA, based on aiming to keep status for the following year.