FastTrack is reporting 629325 users because that's the total number of users on the network (its central server keeps track of that number). Since gnutella has no central server, Xolox can only report the number of users in its horizon, which is probably only a fraction of the real total. When you search FastTrack, your query probably only reaches about the same number of hosts as a query on gnutella (not the entire network for either). I don't know how many connections either Morpheus or Xolox establishes with other hosts by default, but if you have a fast connection it's concievable that Xolox is connecting directly to more hosts than Morpheus is thus giving you a larger horizon (28000 does seem large). If you knew exactly how many direct connections you had (try using "netstat -a" from the dos prompt without any other network applications running) then you might be able to better compare the two networks. At any rate, the total number of simultaneous users on either network isn't relevent.