On our trip to New York we flew with 2 different airlines, using 2 different UK airports. We left Gatwick on Continental and returned to Heathrow on Virgin – this gave us a pretty good opportunity to compare the service provided.
The service on Virgin was much better, including bringing around ice creams half way through the flight, but Continental was adequate, they weren’t rude or inattentive or anything. The entertainment on Virgin was again better, having a decent selection of films/TV/radio, whilst Continental had a lot less options. The legroom was far and away better on Continental. I’m not especially tall, but when a heavy person sits in front of you and moves around a lot it’s a lot less painful when your knees aren’t actually touching the seat in front. According to Global Airline Seating Guide there is no difference, but on our flights (of course, the different aeroplanes may make a difference, between a Boeing and an Airbus) it felt more like 3 or 4 – quite a noticeable difference.
Update: Just spotted that Pete has blogged on a similar subject, and he found SeatGuru. SeatGuru also seems to display the legroom per plane model per airline. Mind you, this claims that Virgin should have more legroom than Continental on the specific planes we used which wasn’t our experience.