Yield is largely a function of light. If you make a healthy canopy that covers your entire grow area, thereby using all (well, more of) your light to grow your plants, you'll yield more than if you have light hitting the floor. It's easier to do that with photoperiods, because you control how big the plants get (by choosing when to flip). It's possible to fill a tent with autos, but you have less control. Genetics and grower skill play a big part, too, but in terms of what's possible in general, photos let you make plants as big as you like.