Thats a tricky one. Yes it will naturally be better on pick up being a dirty fan, but because of the one we owned had the hellish push on bag to dock principle, the bag had a tendency of coming off compared to more modern ones with a bag push in and lock holder.
Regardless of the updated bag holder, the main problem with the Oreck is the airflow/suction channel inside the spine at the back leading to the bag - terribly narrow and a tendency to clog. So although it might have better pick up than a Dyson, the Dyson has more modern and wider suction airflow channels to pass the dirt to the bin.
