Sizing spray just gives the fabric body. Starch makes the fabric stiffer and therefore, easier to handle.
When using spray starch, spray on the back of the fabric as it will leave a white residue, showing up particularly on darker fabrics. Guess this is why I prefer sizing.
Sprays can be used once you have laundered your fabrics before cutting. Use it in place of a spritz of water. And anyone working with minatures, spray starch is a must.
Suzanne