The "square toward the target" stance is better when shooting USPSA because targets are often engaged on the left & right, as well as straight ahead. Moving across a wide array of targets is not as easy with the Weaver stance.QUOTE]
I thought USPSA was a run and gun sort of thing so your feet wouldn't be in any given position for any length of time. i think i perfer my feet with one slightly in front of the other. then again i don't know much about USPSA. i'm also embarassed to say i don't know what a weaver or isosceles stances are. i'll have to Google it to see which i use.
Some USPSA shooters never shoot while moving - running to strategic spots & stopping before firing. The more experienced shooters shoot on the move when possible, but even they sometimes shoot from a fixed position. Some stage setups
require (mandatory) that several shots be made from a particular spot. In fact, some stages are shot from one spot by design.
For GSSF, I had always shot with my left foot forward, much like Bama said. However, in the last couple of matches I have tried standing squarely facing the target... mainly to accommodate my left-eye/right-hand shooting. It's too early for me to tell much difference.