According to the article, Brandt's study was done with a metal cylinder spinning the wheel. The overall picture is more complex than that - rider weight, wheel weight, prevailing wind, etc...
Back to the original topic, swapping Zipp 404/909 tubies for clinchers... the buyer should be aware that the clincher rims weigh a bit more, adding to spinning weight, due to the aluminum rim that must be fitted to the carbon wheel. That will also have an impact on performance. It's never a simple answer.
I bought a used set of 404's in tubie, and just love them. Hard to take them off the bike. Smooth ride, and ever so fast on the downhills.
Yes, clinchers are easier to repair, but curiously enough, the last two flats I had with clinchers were sizeable cuts, rendering the casing useless. Didn't matter that I could change the inner tube easily, the result couldn't be ridden. Sure wish I'd had a tubie tucked under the seat on those days...