You would think from all the moaning here on FT that IB's pitch is some unsurvivable number, but according to SeatGuru it's 32" on all long-haul aircraft. That's an inch more than LH on most of their planes, an inch more than UA on all their planes (not counting E+), and...golly, look at that: an inch more than BA.

Better seat pitch, lower price, and the luxury of not having to connect in LHR seem to make IB the clear choice here. If you don't have any OW status why not sign up for an AA challenge? This might get you a good way there.