I think the answer is obvious.
Against City it had to be a defensive set up, there was no other option, anything else could have been disaster. We were solid in defence and our midfield was forced into a type of game that suits them
Against Brighton we had a different formation which was really neither here nor there.
Iwobi wad running around like a lunatic but was neither defending or attacking.
Patterson was completely exposed from an early stage and nothing was done to address this, in fact Coleman would have been a far better option in a game like this. Patterson against City was a wing back with Godfrey as cover.
McNeill was totally unable to give Patterson and back up and most of our problems came from that wing with nothing done to change things. Even bringing Coleman on to replace McNeill would have tightened that wing. It isn't as if there was an attacking threat from us down that wing anyway.
I feel the same formation against Brighton as had been used against City would have been far better.
I think Iwobi is seen as the attacking midfielder but I didn't see him offering anything in the last game apart from the run for the penalty when the game was long since over.
The manager is trying to pick a team to win when that team at present isn't even confident of drawing.
Look at the City team and performance and let that be the template.