I am not sure if you had seen comparisons like this [1] or not but it has some important points when comparing these two. But I would say it also depends on how you are gonna use the streams. For example, if like us, you are going to digest the streams using Spark I would say Spark's API is more mature with Kafka (unless you have switched to Spark 2.2 and higher).
[1] http://go.datapipe.com/whitepaper-kafka-vs-kinesis-download