How spot on are expertflyer and flightstats in determining the punctuality of flights?

I'm thinking of switching from BA12 SIN-LHR to QF9 SIN-LHR. Having flown QF9 quite a few times I've usually arrived in LHR quite punctually. But EF and flightstats are now saying that QF9 is late 25% of the time with the average delay being 72 mins (!), whilst BA12 only has a 5% chance of being late with an average delay of 8 mins.

I'm trying to fit in a day trip to Nottingham before flying off to DXB in the evening, so the more logical choice is BA12 which seems to be significantly more punctual. Knowing my luck I'm almost certain that I'd be part of the 25% of QF9 arrivals that are late.

But can someone advise me on whether I should trust those stats?