I would make a decision based on the chances of getting an upgrade on US air. If you think you have an excellent chance of getting one, then I would probably go with them since business on US air is probable better than economy anyplace else even if they have better amenities. To me, sitting like sardines is worse than anything else no matter how great the amenities are. However, if you think your chances are not that good or downright low then it's a tough call between virgin and ba - maybe someone else can help you with that!