Cleaning thick carpet isn't easy. There needs to be just enough suction to pull up particles that have settled deep within those long, luxurious fibers, without making the floorhead impossible to push. Too much suction and you'll get stuck; too little and there won't be much cleaning happening.
I recently ran a big group test to find the best cordless vacuum on the market, and as part of that I ran several suction tests on thick carpet. The model that scored the highest marks for cleaning deep-pile carpet was the Shark PowerDetect Cordless.
