I admit that I always thought that it was 92 who were most successful - after all, when you have Tuck, Duke, Kingcombe, Kent et al flying for the unit, it must surely be in with the prize.
However, I then read that when Laddie Lucas (late of 249 oddly enough...) was an MP, he managed to have research carried out that apparently 'proved' that 249 shot down the most aircraft.
Brian Cull gives the credit to 249 in his history of the squadron and comes up with 328 .5, presumably from the F540s and the combat reports in the PRO he cites.
I don't have Aces High to hand so can't check Chris Shores' potted history of all the fighter squadrons to see what he says about this. Any idea what 92 scored? Despite scanning the bookcase behind me twice, everything with the answer in is at work...
On a completely different unit - 11 was the first fighter unit in the RFC, so might have a bit of a claim to stay on the books. I agree, though, that if the RAF is so keen on ethos and heritage issues, that the most famous units ought to be kept on, which would require looking at their achievements from WW1 onwards (which, I guess, would mean 56, 74 and 92 would all have to reappear).