Google Blobstore versus Google Cloud Storage

Better to use the Blobstore. The service has 5 GB of space for free (as of March 2012). The cloud storage is a paid service. The App Engine blobstore is like Amazon S3, but less flexible. It has HTTP-based API and Java / Python APIs (see http://code.google.com/appengine/docs/java/blobstore/overview.html).

If you're starting a new project, I would go with Cloud Storage.

It seems that Google is pushing their Cloud Storage platform harder than their blobstore platform. For example, currently programmatically writing files to the blobstore is deprecated but is supported by Cloud Storage. I can't read the future, but I would bet that Google will be deprecating more and more of the blobstore API in favor of the Cloud Storage API, which will lead to headaches down the road.

UPDATE: Programatically writing to the blobstore is no longer supported, but it is fully supported on app engine. Further, you can use the blobstore API and still use Cloud Storage as a backend. At this point, it's clear that Cloud Storage will outlive the blobstore.

UPDATE 2017: Google's official recommendation is to now Cloud Storage rather than the blobstore. Called this one 4 years ahead.