Not true at all - the problem is that IPv6 routes are less mature and less monitored than IPv4 routes, so using v6 preferentially is actually often slower.
I work with VOIP and we had to disable v6 for our customers because we were getting complaints about latency issues repeatedly from customers on v6. Disabled IPv6, no more complaints.
IPv6 is more likely to make you "the Yahoo of your market" than the inverse, especially if you work in latency sensitive applications.
Facebook and many other companies are finding that IPv6 is faster, personally at home I have found that disabling IPv4 allows me to more quickly buffer and stream Netflix, and about 30 - 40% of my traffic is IPv6. My Apple TV is the last hold-out that still seems to use IPv4 over IPv6 for Netflix.
It's actually not too contrarian - The problem isn't the average speed or what happens when things are working, it's what happens when it fails or when things need servicing. Packet loss and latency or slow response times for servicing of the routes affected our customers greatly. Far more than a small bandwidth improvement would buy us on a service that isn't bandwidth constrained at all.
In large part, this just boils down to the fact that less people use it, so less people notice problems and they're addressed less quickly. However, it makes it very unusable for applications like VOIP to customers when there are issues occurring. So while the bandwidth may be better on IPv6, I have no experience with that side of things personally, we're far more concerned with link stability - packet loss, latency spikes, that kind of thing. Again, just anecdotal, but not necessarily contrarian either.
I work with VOIP and we had to disable v6 for our customers because we were getting complaints about latency issues repeatedly from customers on v6. Disabled IPv6, no more complaints.
IPv6 is more likely to make you "the Yahoo of your market" than the inverse, especially if you work in latency sensitive applications.