I heard Charlie Weis saying that early in the draft he wants guys that score TDs over anything else. I have heard Snead say the same, except that he also wants guys who prevent TDs early in the draft.
Skill positions. RBs, WRs, CBs.
Whether we all might see it that way or not, I suspect that Snead and McVay think that Atwell will contribute this year, probably as a gadget player, (and I also suspect they are going to see if he can be a PR). I also suspect that because they see Jones as a super-leader, very steady, very smart, that they see him not only as contributing but perhaps even as a starter sooner than later.
That is, the development period is short in both these guys.
And, I also suspect that they traded out of the 3rd round into the 4th because the guys they think they need are NOT immediate hole fillers, but rather are developmental depth players.
Who knows if this suspicion is correct, and if they are judging correctly.