I can definitively say that unless Google App Engine has substantially changed in architecture over the last 12 months, it is definitely not faster to host your static site there rather than on an nginx-based VPS with someone like Digital Ocean.
My tests showed load times on GAE-hosted static sites to be around 200ms - 300ms slower than a reasonably-optimised DO VPS.
It's possible, of course, that GAE would pick up some speed if you're loading the page from somewhere a long way away from the equivalent VPS, as GAE essentially comes with a built-in CDN (to the best of my understanding).