Hey guys and girl, I'm not looking for responses like "they're both good in different ways" and other noncommital types.  My question is, if you had to pick one to build your team on, which one would you choose and why?  More specifically:

Over the next 3 years, who will have more success as an NFL running back, Jonathan Stewart or Deangelo Williams?  Feel free to discuss all aspects, including:  age, blocking, versatility, attitude, receiving, scoring, health, work ethic, etc.  I think the question is an important one.  If D-Will is better, we need to pay him and keep him.  But is he?  What do you think?  Which back would you hate to see go, because you see him achieving greatness with another team for the next few years?