IP addresses come in two versions: IPv4 and IPv6. The new protocol version was introduced as we're simply running out of IPv4 addresses. The much bigger supply of IPv6 addresses means IPv6 proxies are cheaper but also less trustworthy when it comes to scraper blocking. In addition, IPv6 support is still uncommon so not every website supports it.
Regarding which is faster ipv4 or ipv6 - any speed differences are negligible when it comes to web scraping.
When it comes to proxies and web scraping, IPv4 proxies are still the most popular choice. However, IPv6 proxies can be much cheaper if the target website supports the new version of the protocol.
For more, see our introduction blog on Proxies in web scraping
