IMHO It is always better to use a standard api where possible. Your own example shows this perfectly. You were able to try your identical code on two providers when one failed to work as expected. Switching to any native API prevents you from doing this.
If using EclipseLink as your JPA 2.0 provider works well for you, then use it. If you do happen to run into an issue, file an EclipseLink bug, and get help on this forum, or the EclipseLink forums and Newsgroups.
