If the OP is not likely to get upgrades based on elite status, then -- regardless of whether he flies BA or CX -- I would probably credit to the program whose miles are most useful for the award travel the OP hopes to redeem for, and/or the program that makes it easier to achieve oneworld status. I'd take a look at both AA's AAdvantage program, and Iberia Plus. (Note that Iberia Plus Avios are transferrable to BAEC for those situations when BAEC offers a better redemption rate, such as Reward Flight Savers for intra-European travel to or from LON.)