Ceiling Motion Detector

It has been some time since I installed a ceiling motion detector. This is a commercial bank (Lobby), the ceiling being about 16 feet high, and the floor area being about 40' x 40'. I do have the choice of using several wall/corner units, that would mount about 10' from floor. What would you use . . . the ceiling unit @16' or the wall units @10'. Also, for each type, what type (such as dual tech. or pir only, and what make would you use, (such as Intellisense or Optex) based on your past experience. Many thanks for your help. Robert