Separate names with a comma.
Is there an audible difference in quality here or am I picking at straws?
Using what? Out of an iPod or iPhone, probably not. Through a TOTL headphone system, maybe, depending on the music.
out of a 4th gen iPod touch with gr07 mk2/ba200 earphones
What Currawong said.
Easiest way to find out is to rip some music to flac and 320 and hear what they sound like to your ears.
Couple of things. Use ALAC on and Ipod instead of FLAC if you don't already have a FLAC library. The other is that there's a free NERO encoder that does AAC 400 CBR. Still 1/2 the size of losses and about as good on your Ipod. AAC400 doesn't work on everything but seems to be fine with the Ipod touch. For flac I use 0 compression level. Very slightly larger file but easier to decode.
I don't know the BA200 but the GR07 only needs 320. It a great IEM but low level res isn't it's strongest attribute. You may or may not here the difference if you find a passage with the right kind of ambient decay but in normal use, you'd be hard pressed to notice. I like Apples codecs on an Ipod. AAC and ALAC.