Davis is a good ball playing centre back but not physically big enough to be imposing in the air. Would do best paired with a big dominant defender, he had that sort of partnership with Gary MacKenzie for us last season and it worked very well. Played well over 100 games in League 1 and still only 26, so I'd definitely say he looks to be a good signing for any League 2 side.
I can also add that Gunning was a disaster in the Scottish Championship too, so at least he's performed consistently in both leagues.
Just out of interest, what do you reckon Grimsby's aspirations for the season are? Eyeing promotion/mid table/staying up again?