If it were me, I would choose based on;
Price
Departure and arrival times that best suited me
Whether the plane was 2-X-2 or 3-3-3
Terminal of departure
I mention terminal of departure as on a short flight such as NYC-LON, I would probably eat on the ground before departure and choice of eaterie is important to me. T4 at LHR for example, is bad. I would then skip the food on the plane.
The rest of the experience is going to be fairly similar whatever airline you choose in terms of seat, food, service & IFE.