The Apexi isnt a dual cone design though, i find it hard to believe the whole surface of the cone is less than a fifth of the oem filter? It must be huge?
The branded aftermarket suppliers will need to produce to some standards, else it would ruin their reputation. The crappy no name ones may be rubbish yes. Plus plenty of tests have been done to show the materials flow alot more air than stock filter material, of course at the expense of filtration, but thats a trade off i guess. The OEM induction box will be produced with noise restrictions, filter restrictions etc... that aftermarket kits wont be.
I guess the only concrete way of testing would be to RR a car with the stock airbox on then again with an aftermarket kit on. I really cant see the stock system being better than a BMC sealed filter with a direct cold air feed though.