You can talk about it for ever but 100% files are much better than words.
No one is questioning whether a MFDB will look better at 100%, full resolution, at low ISO. What's being debated is how relevant the differences are in common real-world image applications such as a typical magazine page or web images.
To go back to the audio analogy, it's to be expected that a $40,000 sound system will sound better than a $8000 system in a soundproofed listening room with anechoic foam on the wall and all of the other high-end acoustic enhancements. But put those systems in a typical living room with traffic noise in the background, a refrigerator running in the adjoining kitchen, and the air conditioning or furnace running, and telling them apart becomes much more difficult. Put them both in the cab of an elderly pickup truck with a leaky exhaust pipe and a diverse collection of squeaks and rattles driving down a washboardy dirt road, and it becomes pretty much impossible. If you're buying a sound system for the living room, it's valid to question what that extra $32,000 is really getting you in practical terms of value for the money, beyond the snob appeal of a catchier brand name on the faceplates of the components.
For many photographers, a MFDB offers little in terms of concrete benefits over a DSLR. MFDB has little to offer a concert shooter that cannot use flash and needs fast, accurate AF in lighting conditions where ISO 1600 is the rule rather than the exception. The same is true of an event shooter covering a horse show who must get salable shots of 25 horses and riders during a 4-5 minute event. Let's see a comparison between a 1Ds-II and a MFDB where both are shot at ISO 1600 and see which one delivers more "dimensionality" or even a usable image, like where the subject is moving and the AF has to track it.