Ok
1. They have WMR, with tools and some of the best headsets on th market.
2. Ninja Theory have experience making a VR game, rare have expirenced with kinect, so they have some good and relevant experience.
3. Will sony's devs have more experience? Yes they will, but this does not necessarily mean xbox devs won't be able to make VR games as good as.
4. Sony have likely lost money on PSVR overall. Sothere devs will gain expirence, but while losing money.
Like I've already said we don't know if Sony launching VR first will be worth it.
Both approaches have there pros and cons.