Two points:
1) EclipseLink goes beyond JPA too. Whatever special features Hibernate has you will also find there.
2) EclipseLink has *far* nicer authors and community support than Hibernate. You will waste days with Hibernate bugs (but don't write "bug" in their forums because they might ban you!), no one will reply to your questions and when you finally get a reply it will be from the authors telling you off. I mean, how dare you imply that their software isn't perfectly? :) True story. I've talked with many other people who've experienced the same.
In short: use EclipseLink and never look back.
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