I would tend to agree, knowing what zookeeper has been doing and actually using zookeeper (and etcd) I can say that the API and the primitives offered by zookeeper are IMHO better (although this multi-version concurrency control model is interesting) and more mature.
It feels like etcd is 'still discovering itself' for lack of better words.
Zookeeper has been around now for over 5 years with an extremely large install base.
Kafka, Hadoop, Solr, Mesos and Hbase projects that leverage Zookeeper distributed coordination.
Zookeeper has already delivered.