Amani Jones, as great of a teammate as he is (by all accounts), couldn't cut the mustard with the mental side of playing LB last year. He was out of position and missing assignments non-stop and got pulled early on in the year. You have to realize that at this level of football being a physical beast isn't enough; I'd argue it's less than half of the big picture.
There's a reason guys like Jewell and Kirksey can thrive at the NFL level while being undersized and not as strong or fast as more athletic linebackers...they're smart and instinctive, they learn the defensive scheme, and they can read offenses and put themselves in the right spots to make up for the physical shortcomings.
With Jones, I'd have to trust Seth Wallace's opinion on who should start over any opinion on this board (including mine). He'll be a DC and HC someday in the not too distant future.