Kind of like comparing apples to oranges, very different places, reall. We have eaten at WP Express many times, and recently ate at the Cafe (May 2010) While we really like the Express, we found the Cafe to be way better - better selections, much more extensive menu, great food & great service.
The only drawback I'd see to the Cafe is if you're there when they're busy it could be very loud in there. We were in there when it was almost empty, and it was still noisy (industrial-chic decor, so noise just bounces off the steel/concrete/tile etc.) Very nice if you can get a window seat overlooking the water, too.