Which subwoofer is better?

The Energy sub is probably slightly superior. uming the specs are accurate, it has significantly better frequency response on the low end (i.e., it can put out lower b frequencies than the Polk), which should enhance your movie-watching experience. And though my sub is front-firing, all things being equal, I tend to prefer down-firing subs. It also looks like the Energy has a solid amp, while the Polk specs don't mention what type of amp it has.