I'm not sure that Lang is really any more experienced than Smith, other than touring with Scotland this summer.
I've also not seen anything from the Cat (having not heard of him before we signed him) to show me that he is a better player than Smith. He's obviously much more experienced, so I guess it's a choice between the more experienced but perhaps less naturally talented player, or the player learning on the job but who is pretty more capable of turning a game.
Smith did struggle towards the end of last season which is hardly surprising. I think if we're continuing to struggle as a team this season then may the Cat is the best person to try to control the game more, but if we're generally playing well then I'd like to see Smith get the starting shirt. Obviously injuries will be an important factor, and I'm sure there will be a degree of rotation as well