Ball-head pins are the most universally used in both dressmaking and quilting. For that reason, you will find them in a variety of lengths, shapes, colors, and designated uses.
From thick (but sharp) heavy duty pins to very thin and very sharp silk pins, ball-head style pins are the best to use in the pattern cutting process and during garment construction for a simple reason: The sphere end provides a safe and comfortable way to insert and remove the pins in both the fabric alignment and stitching process.
Keep in mind that when you machine stitch, every pin is removed as you approach it. Ball-head pins allow for the prefect grip, to safely and comfortably remove the pins in a speedy fashion as needed.
When shopping for pins, you'll find a variety of ball-head pin styles and sizes on the market. Each size/sharpness should correspond to the nature of the fabric you'll be working with.
Thicker, longer pins work well for medium and heavyweight fabrics. On the other hand, thin, sharp pins also known as silk pins, are used with very lightweight fabrics, especially those made of silk, which can be easily damaged by heavy pin marks.
If unsure which ball-head pins to start with, a universal size with a shape and length that falls right in between, can be used with most fabrics and will provide a good initial investment. Later down the road, as you experiment with different fabrics, you can purchase additional pins to fit within more individual fabric and project specifications.