One thing that was noticeable last year when we flew with BA (LGW-MCO) was that they fly from the North Terminal. The North Terminal was a lot more pleasant than the South, mainly because it wasn't anywhere near as busy. I suspect this has an impact on their punctuality as it is a lot easier to get the aircraft loaded and away.
We have flown with VA many times and have been generally satisfied, but BA just edged it for me, although we are travelling with Virgin Holidays this year, so are tied to VA and we also have loads of reward points to use up, so may be a while before we try BA again!
As already stated though, because there really isn't a huge amount of difference between the two, price should really be a good factor to consider first.