I actually thought Allen's best game of the season was when he played deeper as one of the two holding midfielders (can't remember who against, Swansea maybe? Not sure)
He isn't good enough at this level, nor is Shipley.
If you play Shipley he's generally more anonymous and gives the ball away a lot, but does carry a bit of a goal threat.
If you play Allen he has no goal threat and doesn't look likely to pick up an assist, but he's a bit more involved and can cause a bit of a nuisance popping up between the lines.
Neither option is great.