Earlier quoted context omitted.
eventual consistency is a bad choice for a messaging platform Strange you would mention that in the context of Cassandra, since it allows for per-read/write configuration of consistency, from "eventual" to "strong". You get exactly what you ask for with Cassandra, whether its availability or consistency. AFAIK, HBase only supports strong consistency.
This is not the main reason people would choose HBase. For time series data HBase is much better at load balancing the data and at storing the same data in sequential blocks so that in a single operation you can fetch all of the data points that are interesting. Cassandra supports range queries but the last time I saw it wasn't super awesome at load balancing data across nodes when using the OrderedPartitioner. Do I…
http://rubyscale.com/blog/2011/03/06/basic-time-series-with-...
http://www.datastax.com/dev/blog/advanced-time-series-with-c...