Hello,
Both SZ02 and SZ03 will be good for IPO and for walk. Difference in price arises from the different kind tape and sewing. SZ03 is more complicate to sewing and more thick, SZ02 is a little more flexible but funcion is same. SZ03 have available more tone of colours but if You want violet, SZ02 is available in this colour. (difference in tone of violet and kind of sewing between SZ02 and SZ03). Harness will be adjustable on many holes but still need "shoulders" and chest circumfarence and neck circumference. "Shoulders" maesure on 2 parts in place where dog have top part of harness.