Totally different player. McGeouch is the water carrier of the team. I'd liken him to Guntveit, don't realise what he brings to the side and the work he puts in until he's gone.
Scott Allan wouldn't fit into Aberdeen IMO even if we were interested in him.
I'd love a proper left back or another deep defensive midfielder to allow Shinnie to slot in at left back. That would really strengthen the back line.