A. A. On normal LAN and fast WAN links you are unlikely to see a real-world difference in responses times between any of the net-libs - this is due to the fact that network response/number of packets is not significant in these environments compared to application/database/server responses.
However, on slow network connections - anything from 64Kbit/sec and below can be considered slow - then you will see a performance improvement if you use the tcp-ip sockets net-lib.
Contributed by Neil Pike