I've been told the same thing about dishwashers; all the pumps are the same and you're just paying for more buttons. They did add that sometimes the top-of-the-line model will still actually clean better due to some added sensors that will extend the cycle if the water through the pump is still getting dirty, but it sounded like the improvement was negligible.
Unfortunately everything is getting more complex. Even my dirt cheap "buttons and knobs" washer no longer has a batch size knob, instead incorporating some sort of sensor that determines the "optimal" water level.