Google app engine or Amazin ec2 for Restful services and direct access to datastore

I'm thinking of building a Restful app on either App engine or ec2 de开发者_运维知识库vloped in Java. I'm interested in opinions/experience of using the two options for this. The primary purpose is to create web services to write and retrieve data through a mobile device...basically creating an API for the service I want to create. It seems to me it would be quicker and cheaper in the beginning to go with google app engine using either restlet or grails.But I also think that I could run into problems in the future when I want to so somthing more advanced and might be restricted by app engines environment.

I also want to be able to do data analysis on the data in the datastore as well. It seems that with app engine this would be hard as I don't have direct access to the datastore ( in Amazon I could still have access to the underlying db if I go with MySQL ) .

Do you actually mean 'direct access'? Your question implies that you want to write an API, which is quite different.

If you do want to write an API, I would recommend App Engine*, and simply replicating (via your own code or the bulkloader) the data to a local database you use to do reports, etc.