McGrath has lower speed than Tate; does it mean we should take Tate over Mcgrath. How you could select new player who have no experience or little experience. Domestic performance! Look what happened to Dickens, Shanto after successful domestic season. how you could compare JO with Mehrab. JO has better average (I presume) but Mehrab can play as middle order also; plus he can bowl.
It is not possible to develop a transparent system for selection though cricket is a game of numbers, numbers do not tell everything.