I heard from some people at the RIP64 conference that for them, IPv6 is faster than IPv4.
The question is: is this because IPv6 is routed differently than IPv4? Is it because it travels through dedicated IPv6 links which are currently much less loaded than the IPv4 links?
There are still problems with some routers processing IPv6 in software instead of in hardware, so I find it hard to believe that the speed difference is due to routers finding IPv6’s fixed size headers that much easier to process and route. In many cases, IPv6 is slower than IPv4 because it is tunneled through IPv4.