I've flown quite a few times with both BA and Virgin (most of those to New York though). We've flown from LGW to MCO once with BA and that was 2006, and it was all good. In 2004 and 2011 we flew direct with VA (and in 2008 we flew via Vegas, to get married, and then home from MCO to LGW with VA).
I've never had a problem with BA. In fact they came to our rescue when a US Airways flight from MCO was cancelled. And they got us home in the midst of the NY blackout in 2003.
We have chosen to fly with BA this year, as DH prefers them. I don't recall ever having a delayed flight with them, and certainly nothing cancelled. VA have cancelled on us once (a flight to NY) and we were delayed going out to MCO last time.
BA happened to be cheaper this year than VA, and we also bought our tickets during a sale (2 adults and 2 children for £3,600). However, I did receive an email last week saying our flight time had changed from 11:20am to 1:40pm which was really disappointing. But I spoke to a really helpful man on the BA helpline as I was concerned they might add an earlier flight in the meantime, and we'd been bumped to the later flight. But he assured me that we are on the first flight out, regardless, and if they schedule and additional, earlier, flight that day then we will be on it.
It does mean we can't check our bags in at DTD, but we've only done that once and it really didn't make much difference, we just didn't need to be at the airport quite so early.
The only other thing that I was disappointed about was BA's 3-3-3 seating plan (as opposed to VA's 3-4-3), as it means the 4 of us won't all fit in one row. But I'm hoping it means a bit more room instead.
All in all, it's 8 hours trapped inside a flying metal tube, and I don't think the service differs much between them

it's just individual preference.