DM position is very sensitive nowadays a bit like CF/SS.. many teams don't use this old traditional target man ala Ruud /Toni but play the likes of RVP,Rooney,Higuain upfront..
so we can argue all night about the likes of Essien vs Busquets but both do the same job except the former do more in the teams attack . we have seen teams like Germany and Holland effectively use people like Khedira/Bastian as the 2 players in 4-2-3-1 or Van Bommel with De Jong.. both teams reached the WC semi-final
Cambiasso is now sitting in the traditional DM position all alone but with the new roles i'd also put the likes of Essien , Banega,VB..etc with him.. hard to pick one as the best IMO