Survival of the fittest. It applies in the wild, and it applies in the business world. The companies that survive and thrive must possess something that others don't.
Pretty much every company will say that it has competitive advantages over rivals. Although those advantages aren't always all they're cracked up to be, there are some businesses and stocks that do enjoy strong competitive advantages.
Healthcare is a sector where the differences between the truly great businesses and the mediocre ones can be especially pronounced. Three healthcare stocks that I think have a killer advantage right now are Abiomed (NASDAQ: ABMD), ShockWave Medical (NASDAQ: SWAV), and Vertex Pharmaceuticals (NASDAQ: VRTX).