Question is clear as you see in the title, it would be appreciated to hear your ideas about adv./disadv. differences between them.
UPDATE: I have decided to use Hazelcast because of the advantages like distributed caching/locking mechanism as well as the extremely easy configuration while adapting it to your application.
Answer
We tried both of them for one of the largest online classifieds and e-commerce platform. We started with ehcache/terracotta(server array) cause it's well-known, backed by Terracotta and has bigger community support than hazelcast.
When we get it on production environment(distributed,beyond one node cluster) things changed, our backend architecture became really expensive so we decided to give hazelcast a chance.
Hazelcast is dead simple, it does what it says and performs really well without any configuration overhead.
Our caching layer is on top of hazelcast for more than a year, we are quite pleased with it.