I have taken depth of water into consideration. I personally think that most reservoirs are deeper and bigger than most lakes and I think way more fish also. With being more fish they need more food and that means traveling more and always on the hunt for food.
I think that current has something to do with it also. Reservoirs are made by dams and they let out the water creating more current than in a lake. It would have to do something to the condition of the water.