I'd take a full back who's excellent defensively but average going forward over a defender who's excellent going forward but average defensively. Provided we have a good attacker down his side, I don't think his lack of attacking capabilities will be that big of a problem.
The thing with modern day footballl is players are pigeon holed into a position at a very young age now. Those positions are also very specific. You cant just have a lad who is a midfielder, he must be a Dm, AM, LCM etc etc etc. This can result in players not full filling their potential, or certainly not showing all of what they can do. Anderson being brought up as an attacking midfielder but us trying to show horn him into a defensive midfielder for example.
With shaw, this is a positive thing. He's a left back. Its clear that he's been a left back from the very first school U8's game he played. As a result, even at 19 years old. He knows the position inside out.
I personally think he's an excellant left back and one that will only get better. I agree with the consensus that he offers more in attack when he has a winger infront of him. He's not exactly lightening quick or as tricky as an ecra say but he makes the right choices when attacking. So when he has a winger infront of him, he knows when to overlap, when to use the wingers run and cut inside / carry the ball.
Fingers crossed him and rojo stay fit and continue to improve. If that happens i'll be happy that the left side of our defence is taken care of for a good few years