When you make a 4PP w/ triangles you only have one option for laying out the pieces, all 90' points to the inside. So if you are indecisive or don't want to agonize over which layout is the prettiest that is the way to go. If you make them w/ squares you have 4 different options for each stack (4 90' points) that can be a better option if you have a tight repeat and want to minimize how many duplicates you are making. You can also minimize the duplicates by choosing a strip size not evenly divisible into the repeat size. (if your repeat is 8 inches go w/ an odd number like 3 inches)