I've seen a bunch of MP3 vs. AAC articles out there, but this one seems well-written enough and is getting enough blog karma that I thought I'd post it. The spoil the goods, the reviewer gives AAC the edge, though he also points out that you need at least 192Kbps AAC to be "Good." Most of his analysis comes from studying the harpsichord - though a lot of his comments seem similar to what I hear when I listen to cymbals in live recordings. I usually record my stuff at 256Kbps MP3 for portability, which is good enough for my concert-damaged ears.
Encoding Observations