I think it is based off his potential coming in. He definitely has NFL size. He was injured some last year but as you pointed out they have close to the same carries and Boom's stats are much better.
If Hood stays healthy I think he will be a premier back, Boom already is and he must stay healthy as well. NFL goes with Hood on size and potential over Boom though even if they left today IMO.
The key word in this is potential. Potential goes two ways though. I do hope the kid has a good career, I will say that.