I know most people hate PFF, but it is another data point. Surprisingly, Pryor had a better grades than Jackson last season, even when he was in DET. Pryor graded out at 69.9 and 78.1 in Pass Pro. Jackson's overall season grades have been 67.6 with the Rams, and 61.0, 66.1, 69.3, and 57.0 with the Lions. Looking at his grades, he seems more of a road grader and is better at run blocking than pass blocking.
So it will be interesting to see what they do with him. A 6th is nothing, but his cap hit is. Is he playing Center like he did for the Rams or back to Guard?