Headfones?
I got some MDR-EX51 ear buds, they go in the ear canal,they insulate noise, and have a very good frequency range 6hz to 23khz. Just have to make sure you use the right size insulator and postion them correctly in your ears, if you use these in a noisy environment, they're perfect.
To answer your question, I listen very closely to music, and it seems that the iPod has a worse equalizer/amp and some of the lower range sounds and very high range sounds aren't properly displayed. I turned the EQ off on both to test this, the Bass Boast on the iPod is very bad
Edit: I did have some static w/ the previous headphones while using the iPod, I'm guessing this has something to do w/ the metal contact of the mini plug contacting the metal case of the iPod (I have a 3G 15gig)
The newer ear buds I got (discribed above) has a smaller surface in which it contacts the metal housing of the iPod