I normally shop across all 3, Kmart & Big W can be cheaper for some things but the quality is more variable and lots of things have those horrible spray on pictures that crack in the dryer.

Target on the other hand has a much better range, but it is a big of a problem locally because they don't seem to have twigged that there was a spike in the birth rate 6 years ago, and so there's often next to nothing in my DDs size. But I still think for one stop shopping you would do best there.