Unless you can hire Cassandra engineers who have enough experience maintaining clusters, or you can afford to pay DSE to do that for you, working with Cassandra will be quite the burden.

The advancement of PostgrSQL has been amazing, and much credit is due indeed to the NoSQL community’s innovations. I cannot comment of MongoDB except to say that it is quite different than Cassandra.

To summarize, be sure you really need Cassandra and are able to dedicate the appropriate resources to it before taking the plunge.