Look at Harris's most productive years. He was always paired with at least one established playmaker. Hayward and Burks can become those players, but they aren't the rocks that Harris needs to thrive. Imagine, however, if we were to bring in Hinrich -- a player that knows his game, stretches the floor, and can distribute/create a little off of Harris's drive and kick. If we are ALWAYS able to pair Harris with a Hinrich, or Watson (with Harris playing more of a combo 2), and/or Hayward, then, IMO, he'll get a lot more comfortable and effective.
It's Bell. Harris has more in the tank.