Ned Roundtree summed up my same current situation with this topic pretty well...
In LFI-1 with Massad Ayoob we were coached in three stances: Isoceles, traditional Weaver and modified Weaver. (The qualifier course of fire later had portions specified in each.)
Though Ayoob is known as a proponent of isoceles for many good reasons (the position many will revert to under extreme stress, minimizes exposure for LEOs wearing armor, solid platform, excellent and even absorbtion of the recoil impulse, etc.), he actually encourged us students first to find which stance worked best for each of us most of the time; and then directed us that, sometimes, you might need to suit the stance to the immediate task at hand.
A simplistic example would be when an isoceles shooter is kneeling near cover and gets surprised by a threat to the left side. Then, a modifed Weaver is quickest and allows the most reach with the pistol.
American Handgunner's "Tactical Annual 2001," on newsstands now, has a well-written piece on this very topic by trainer Andy Stanford. Titled "Evolution of a Stance"; check it out.