"Security devices (like firewalls, IDS, etc) for the IPv6 world are not available and/or do not offer the same capabilities as their IPv4 functionalities."

This argument addresses the shortage of IPv6-capable hardware and software in the security area. Also, it questions the quality of the IPv6 solutions that are currently available. IPv4 hardware has been around much longer than IPv6-capable hardware, so it can be expected that the IPv4-based hardware is more mature in robustness and functionality.