Before taking it back and buying another one, which backing plate and pad you are using? The gg6 is a much smoother machine and worth the extra money purely on that factor alone. Not to mention the exceptional customer service you get with the folks at griots. That said, the HF DA is way more powerful than the 7424xp but if you aren't using a quality backing plate & pads then that is most likely the culprit.
Try the Griot's 5 inch backing plate paired with a flat buff and shine pad and make sure it's centered perfectly on the backing plate. Also, there's no reason you should ever really need to go over speed 5 with that polisher.