Option 1. If you're looking at the AA flight, check the seat map before finalizing your purchase to see if they offer MCE (as mentioned) or just "Preferred Seating", which really isn't anything special. If it's MCE, and legroom is important to you (it's my overriding factor), then go with AA....

Counter to that, though is Option 2. If you are Silver/Sapphire or higher on BA, there's a chance you'll get moved up to WT+ or get offered it for £100 more or so each leg as the date approaches. WT+ isn't amazing, but it's definitely preferable, and the extra tier points are great.