Good stuff Nik! ^_^
I'm under the impression that Shin has a modest advantage in terms of raw strength and toughness. Speed seems close enough to call even. Skill is harder to judge, but they both seem like "will murder ur face" kinda dudes.
Straight sword fight? I would give it to Shin. Geralt will make him work for it, but seems like Shin has the edge here.
Magic involved it gets harder for Shin. Like, MUCH harder. Geralt can spam about 3 Arda force pushes from what we've seen. I imagine the first one sends Shin flying, but doesnt hurt too much. Maybe Geralt takes the extra distance as a chance to drink a potion or whatever. Any close range Arda are going to hit Shin like a truck. They have shattered a stone floor roughly a foot thick.