Well it very much depends on how the beater gets its energy, most seem to use the airflow which obviously reduces the suction and also means that sometimes 'stuff' gets trapped inside the turbine. One other thing I had not realised when I bought my otherwise good Vax was that the base is so low to the floor that it hits those edging strips at doorways for th carpet, resulting in great gouges taken out of the cleaner bottom.
Brian