Couple of things that were forgot.

1. Gnutella has more 192 kps songs and more whole zipped albums, but as said above Kazaa has way more total music because it is so much bigger.

2. With Kazaa you are way more likely to get sued by the RIAA, since it is currently the biggest network and the RIAA always goes after the biggest first.

3. Gnutella is more diverse, Kazaa is mainly music.