Not sure how it compares, but thumbor is fully extensible. There are people using it with HBase, others with Amazon's S3 and Cloudfront, others with filesystem based solutions and yet others with redis or mongo backed images.
Other than storage, you can extend loading images from different places, as well as changing the imaging library thumbor uses.
You can also extend the filters or the detection mechanisms.
Anyway, good to know about magickly.