If you want to know what is the difference between these two MPP databases I recommend reading the following post.
currently both are using Hive query language HQL and use its metadata store. They have great performance yet they do not support user defined functions. In the near future all the current limitations will disappear (more serializations will be supported as well as UDFs) and there will be no REAL use case for using Hive.
I know that there is working going on to improve Hive’s performance (X100) but we have to wait and see.