Osman's technical skills > Coleman's technical skills. There really shouldn't be a debate there. I'm not one to shower praise on Osman, as he frustrates the shit out of me most of the time. But, I have that frustration precisely because he is so technically gifted, yet wastes perfectly good chances that many peoples' grandmothers could put in the back of the net.
That said, I don't think Gatt would be expensive at all. Probably a negligible fee, considering he's coming from the Norwegian league and hasn't really made much of a name for himself yet. I would assume he'd cost us £1-1.5m tops. Yet, for a player with a lot of potential upside on our weak right side (when Mirallas is injured), it would be an excellent buy.