Even though you may never have considered yourself a Women's size, there are times in which you might feel sad or bewildered and need comfort. A Women's size is designed to flatter.
If you have an ample bust. If it is difficult to find a relaxed fit and/or you see fold lines from the shoulder to the buttons. If you weep and seek more ease of movement. Remember: a Women's size is cut generously.
If the buffet makes your palms moist. If you are (at times) unstable and/or insatiable. If you huff and puff. If your thighs chafe. If you take cheery pleasure in warm cake and cheese. If you are disproportionately broad.
If you are fuller through the waist and midriff. If you are often full, or never full. If you have inadequate control; you might be a Woman. A top in a Women's size will give you a more comfortable fit.