Ok info on the "flap"

The impellar on any given pump starts in a random direction each time. The design on the Eheim understands this so the direction the impellar is spinning doesn't matter. For some unknown (and annoying) reason, the aquabee has to have the impellar and flap line up for it to run correctly.

Example (this is all hypothetical):

The Aquabee's impellar starts in a clockwise motion so the "flap" has to cover the right side port for the pump to run effectively. When it doesn't switch like it's supposed to, you get bubbles but the foam doesn't travel up the neck at all, it just pops.

As to if it's worth getting, I would choose Eheim pumps over Aquabee's any day of the week. That being said, the Aquabee still works. I'd base your decision on customer service personally. If your DAS skimmer pump breaks, who gets you a new one?