The main advantage of using IPv6 over IPv4 is the vastly increased addressing capacity. IPv4 supports around 4.3 billion unique addresses, which are rapidly being exhausted due to the growing number of connected devices. In contrast, IPv6 can accommodate approximately 340 undecillion addresses, vastly improving the potential for global connectivity. This expansion enables more efficient routing, enhanced security features, and better support for modern applications, making IPv6 essential for the future of the internet.