For me an important difference is that Cassandra is operationally much more straightforward - there is only one type of node, and it is fully redundant (depending what consistency level you're using).
This seems to be an advantage in Cassandra vs most other distributed storage systems, which almost all seem to require some "master" nodes which have different operational requirements (e.g. cannot fail, need to be failed over manually or have another HA solution installed for them) Mark
