Omar hands down. I liked about every decision he has made and almost every deal has been very useful for the Mets like the deals of Baltran, Santana, Wagner, Perez and many good decision has been pay off greatly. I think the most important decision making is to see the talents most useful or hidden in the players. Money can buy talent, no doubt about it but everybody can do that with minimum effort in researching in the scouting reports (or in Cashman's case, just get the most expensive ones.) It is the sight of the future that is rare in the general managers.
Oh, by the way, Yankee's farm system is one of the best???? You are kidding me, Rangers' and Rays and Braves' are way better in both talent and quality. HIstorically, yeah, it is one the best because all the young kids wants to be the Yankees, it is nothing to do with the GM. It is the reputation of the organisation that build it, nothing to do with the management.