Alright, now look at the logistics of this. Get all the top brands of mowers, (even then all of their decks!) do you compensate for deck size? (ie walkers, 36, 48, 52 all cut differently) Bagging or discharge? Are the decks set up the same? (spacers, spindle height, deck height etc etc.) Do all mowers have same HP? More power, better cut? What grass? Dry, wet, thick, thin, warm, cool? mowing speed? soil composition (ex sandy soil?) Mowing speed?
Essentially, what Im trying to say is that no unbiased test can ever exist. Different power, different deck setup, different operators and different conditions all effect cut. For example, my exmark metro, fixed deck. I can cut at 3" in a multitude of different ways, by moving spindle spacers, deck pitch, caster spacers, and rear axel height. Now, only one of those performs optimally for my conditions. However if I were cutting different grass, the case might be very different. No deck is better than any other really, they all cut grass, and for every place a mower cuts poorly, I can show you somewhere it is the best available.
Even further, many people can confuse good stripes and a good cut (here at least). I see guys around here who have their decks up really high, and their super high lift blades as low in the deck as possible, resulting in a TON of vacume, and amazing stripes, but realistically a very poor cut.