The most noticeable difference between IPv4 and IPv6 is that IPv4 uses a 32-bit address and IPv6 uses a 128-bit address. While there may not be a speed-related difference IPv6 has more qualities such as a built-in network security layer. IPv6 came along due to IPv4 unique IP addresses running out. One reason that the transition is slower is that IPv6 is not compatible with devices with an IPv4 address. To use IPv6, IPv4 4 still has to run which increases operation costs that many companies do not want to invest in.
Resources:
Duò, M. (2023, October 18). IPv4 vs ipv6: What’s the difference between the two protocols? Kinsta®. https://kinsta.com/blog/ipv4-vs-ipv6/
Melanie. (2023, January 12). Why isn’t everyone using ipv6 yet? Hostio Solutions. https://hostio.solutions/blog/why-isnt-everyone-using-ipv6-yet/#:~:text=IPv6%20was%20not%20designed%20to%20be%20IPv4%20compatible&text=A%20solution%20to%20communicate%20with,t%20always%20willing%20to%20pay.