My team at Parse.ly also did a benchmark comparing pykafka (pure Python) to pykafka with the librdkafka C extension enabled. That C module is clearly a huge win for Kafka consumer/producer performance on Python and other dynamic languages.
http://blog.parsely.com/post/3886/pykafka-now/
Unfortunately, as the OP illustrates, there are now 2 widely-used Python + Kafka drivers (pykafka and kafka-python), and as of recently, a third, confluent-kafka-python, which is a thin wrapper over librdkafka.
The reason there's all this fragmentation is because Kafka was quite the moving target for non-JVM languages for the past three years. We have used it in production since Kafka 0.7, so we've had to live through it all blow-by-blow. I'm hoping that with Kafka 0.10 recently released, we can finally unify the community around a single driver (somehow).