If those are your options 100% Virgin. Best airline i've ever flown with.
Little trick tip: Look to find a suitable Virgin flight, then got continentals american site and look for the exact same time. They are partner airlines, so if there's availability, it'll show you the virgin flights listed as 'operated by virgin'. Flight price will be a good deal cheaper than booking direct - plus, as it's a US carrier you're booking through, you'll get the protection of being able to cancel your flight fora full refund - should you need to.
If you can't get a Virgin flight, look at US carriers. They have to deal with big fat Americans so the seat pitches are bigger. I'm 6'3 so also have problems on planes. What ever you do, DO NOT fly BA. Tiniest little seats in the world.
United will likely be cheapest, but the aircraft are very old and don't have posh entertainment systems. It's the old tape based system, so no pausing or choosing what you want to watch. You have to wait for it to re-wind!