AppEngine: database annotations JDO or JPA

I am no expert and frankly I don't understand the differences, but
looking at the following comparison it SEEMS like JDO is a better
choice...

http://db.apache.org/jdo/jdo_v_jpa.html

One of the concerns would be switching back to Hibernate some day when
DataStore upsets me (and it upsets me a lot).

Please let me know what you decided to use yourself.