Nice comparison. Not entirely sure how anyone might think an IR might not involve the air between the speaker and the microphone, as well as a proportion of the space the IR is recorded in. There is no physical way of recording an IR that doesn't include that, at least to my knowledge.<snip>
I can't hear much of a difference even focusing on an isolated guitar track, so I definitely wouldn't be able to hear the difference in the context of a mix.
I thought they were a cute trick when I first came across them, especially as a student of Fourier transforms and convolution a few years back. I'm even more of a full convert nowadays, as I've discovered IR's that actually feel like cabs I own and love, as well as sounding like them.
Liam