Your question makes me think. Here's my subjective answer: I have not noticed a significant difference in the sound quality (remember--not an expert). It is still excellent. But I am quite sure there is noticeably less intrusion of ambient noise. It does not filter as well as tight-fitting in-ears, but I don't like those--for my use, hearing my name called is better...wife doesn't slap me when I don't answer.
I remember reading about some differences in sound with slight earpad mods -- using rubber rings, or different foamies. One thing I remember was someone saying the extra distance using rubber rings (and remember these are way closer to the ear canal, so slight differences could matter) helped bring out the midtones. I myself am a *huge* advocate for Radio Shack foamies over the stock Sennheisers on the MX500. Such a seemingly insignificant change brought much greater mids and bass. I wish I knew a euro-equivalent of Rat Shack or those pads, so I could test that with the MX471.
And that's the fun of modding, right? Finding and playing. I bet the mechanical bass toggle does something interesting with those pads, too.