well, to answer what was probably the intent of the original question, without going into details, hows this:

Honda built its DOHC engines to make more power than its SOHC engines--thats pretty much it. They could have done a number of things differently, and theres nothing definitively or inherently superior about DOHC engines in general--just in the realm of hondas(as with many modern car manufacturers), DOHCs are more powerful.