Kafka has very poor tooling in my experience (a folder full of fairly buggy bash scripts...), and due to ZooKeeper requires a lot of operational care. For example, it's extremely easy to destroy a Kafka cluster by bringing a new, empty ZK server online with newer but incorrect data in its volume. ZK will happily trash the entire cluster thinking it has new instructions. So network isolation is key, which, while obvious, is another source of potential failure.

Kafka also has the JVM, which requires a lot of love to scale in my experience. I do not want my programmers messing around with GC options when writing to what should (to them) be exposed just like a regular file handle (except distributed across many systems). I strongly prefer to avoid Java applications at all costs - in my experience it takes years and years and years for Java based infrastructure to become relatively stable & reliable (see ElasticSearch 5.0, or ask anyone who has been oncall for a Tomcat based application). This is almost certainly personal bias, but it's my bias regardless.

Redis also has a _massive_ number of tooling / monitoring / ecosystem advantages, including hosted options, and can run on a single instance without configuration changes from the developers perspective.

I also have personal reasons to prefer Salvatore's work over the work of Confluent.