This is simply not true. What is true is that Cassandra supports weaker consistency models than hbase in addition to the strong consistency model that hbase supports (and in fact, requires -- you can't turn it off).

Hbase has it's place, but "consistency" isn't a good reason to pick Hbase over Cassandra. Rather, particular workloads can (currently) be done faster in Hbase than Cassandra, due to locality assumptions with how writes are done in Hbase, and the nature of those writes.