Originally Posted by
Cw novice
Worth noting that with Silver on AA you will get:
Flagship Lounge Access (Where available), Soho in JFK. Also if you fly AA from LHR you will get CX lounge preflight
MCE for free on AA with Silver is a good benefit too.
Personally get your 4 eligible flights in SH Y and then do the transatlantic flights on AA.
What will your main Transatlantic routes be btw?
I think BA Silver gets Greenwich access at JFK, not Soho. Soho is the Oneworld Emerald lounge so you'd need BA Gold. AA Platinum also gets free MCE.
Aside from the earning/redemption/qualification points others have mentioned, I would say the main tradeoff is whether you prefer US domestic lounge access (in which case you'd want BA Silver) or the possibility of domestic First upgrades (in which case you'd want AA Platinum).