I think the main problem for Rose is that he can't tackle. Call me old-school but as a fullback you are first and foremost a defender, and as a defender you need the ability to tackle cleanly for most of the time and b aware in your positional play. Rose has good pace and strength, and is ok going forward. But when he loses the ball he also tends to lose his head and dives recklessly into tackles. It's almost a miracle he's not been sent off in a game yet.
Rose is a good squad player, and i think he has developed his game since last season. But in my opinion Davies is the better option, at least defensively. But then again, I'm not the manager.