You get more benefits the higher the annual fees you pay for the card... so you ultimately pay for it all anyway. The question comes back to how much you intend to spend on the card. If you're churning through £1k vs. £100k in expenses per annum, that makes a big difference to whether it's worth paying out for the supplementary Amex membership schemes. If you do a lot of business travel on BA, the BA Amex card isn't too expensive and allows you to accumulate points pretty quickly.
