Strictly personal preference, but generally a thin needle works best. Most important is length. I have a small hand and prefer a #12 John James Sharp. Lesson learned when teaching a class. A lady in class was trying to use a 12 and her stitching was terrible. The next morning someone in class had a longer needle and her stitching improved immediately. Her hand was very much larger than mine so she needed the additional length. So as sharp and as thin as you can get to fit your hand.