Let the code decide what number of servers is optimal for you and the network. Both Pro and Basic can run as either Ultrapeer or Leaf, if your connection and OS are capable/fast/stable enough. LW has code that decides whether to act as an Ultrapeer (supernode) and help route connections, searches and the gnutella traffic that keeps the network working.

Life as a leaf (one of the 30 or so connected to each Ultrapeer) is pretty good. You get the same advantages in searches, but depend on the Ultrapeer to shield you from irrelevant results and traffic which can flood your connection.

Running as an Ultrapeer uses up about 6 KB/s up and down, but has to handle many more connections.