Ok, Surat-Guy
Its good to see a detailed reply come instantly...
Unfortunately I still will not be able to give you the answer you need. That is because the answer can come only from understanding of the business. However, I see you have removed HR Manager from the equation.
So you need to analyse, what is the position for. What is he expected to do. A COO will look after the operations, leaving you to focus on policy / direction and on business development. Actually, coming to think of it, all 3 people are expected to do the same thing, so the difference is in where they stand in the organisation.
Giving someone a COO position tells your team (and outsiders) that he is a decision maker and he is only next to you in the organisation. If you have a Manager, it means he is supposed to look after or ensure proper working, but you are not giving him the same level of decision making. At most he has disciplinary powers. There may be other managers or senior managers in the organisation then he will be at the same level and he can not directly override them
From an external perspective also, anyone meeting a manager knows he is higher then the rank and file but still a junior and not a decision maker. it affects the way people look at him
I am sure you also need to look at costs, in which case if you feel a manager meets your needs, and saves you massive amounts, you need to do that (A COO will ask for lakhs per month, specially if he has come from a well run organisation. The other point being your inability to attract such a person to you.)
An executive, take it out of your list, people will to listen to him