Not all the VR experiences will be AAA games. There are plenty of mobile and desktop indie games that are engaging and don't require state of the art performance (see GearVR). Also WebVR content doesn't rely on traditional DOM rendering that it's the main bottle neck for web applications to feel smooth.
Yes, WebVR is more performant (many webpages struggle to achieve even 60fps). But minimum 90fps, at a much higher resolution is a challenge even running on bare metal right now. And that is needed for even the simplest VR experience (unless you don't move your head that much, but then what's the point of VR).
True, the 2D web may have had its performance issues, but the 3D web can actually be surprisingly performant. Browsers with the new WebVR API implementations can maintain high framerates starting with 90.
I'm running a DK2 on a GTX 660Ti and, now that there are more games that support VR, I'm starting to get those stutters. It breaks the experience entirely.
