You CAN get higher bitrates with Kazaa (or Grokster, which is the same), with just a little tweak. And they do have the the biggest # of users.
Make sure you use the «lite» versions though, without the spywares.
I usually keep Grokster + a Gnutella client installed.
-In any case, Scorbing, learn all about it in great details, with articles detailing each option, as well as a forum like this one dedicated to P2P. At Zeropaid.com
When Napster closed down I tried winmx and Kazaa. With Kazaa coming out on top. then i started hearing about the spyware that is in Kazaa so I downloaded Adaware and saw for my self that it was full of spyware. Then someone told me about Kazaa lite so I downloaded it done the search with adaware, NO SPYWARE.