I'd be interested to know why the OP never considered Heroku
Heroku is hosted on AWS, and so you inherit the performance, but lose the ability to control it (no way to select local SSDs or enable IOPS, as far as I know, for example), while at the same time paying a large premium for the convenience of using their platform.
Just wondering what kind of work he's doing that took him from AWS straight to GCE without stopping to think about Heroku.
Maybe you've hit the nail in the head, he's writing to disk a lot for some reason?