it depends on how you shoot. if you shoot with one eye closed the weaver is best. if you shoot with both eyes open then switch. with the weapon centered off of your nose with both eyes open you will shoot much better. you have to get used to the sight picture and reconciling the target within it. i switched to both eyes open and the iso stance. i found much quicker sight alignment/front sight on target. i find that the weapon naturally is pointed at what your looking at where with the weaver it is off a bit requiring stricter discipline with sight picture.
if your dominate eye is on the same side as your dominate hand and you shoot weaver the sight and target alignment will be fairly close. the iso stance is much faster also.
there is a reason that most competition use the iso or a slightly modified iso stance