The easiest way is the way I did it, to measure the inlet air temperature and then the air flow for each of the setups whilst on the open road. That way you can see which type of filter is restricting air flow and also which is suffering from heatsoak.

OK so I only did it on a lowly ST200 not a mighty Cosworth but the way of testing should be the same and will give give more useable results than on a rolling road. There are so many factors to take into account on the rr that not everyone is ever going to agree on the best solution.