3. Better security. IPv6 was designed with encryption and authentication in mind. IPsec is an optional security component of IPv4, but in IPv6 it is mandatory. With IPsec each individual data packet is encrypted and authenticated, making many of the malicious attacks plaguing the Internet today impossible -- or at least substantially more difficult.
4. Better performance. Changes have been made to the way IP packets and headers are formed, and to the way IPv6 routers process the packets to improve performance -- resulting in fewer missed or dropped packets, and more reliable and efficient connections. With more people and devices sharing the Internet, and higher demands for VoIP and video streaming, performance will be more critical than ever.