How though? In what way? Neither are particularly fast. Both are balanced in that they are solid defensively. Both good in the air for outside backs. Both score the occasional goal, but often from distance as I don’t think either get into the box often. Decent crossers of the ball. Digne is rather strong on the ball, not sure about Tierney. Tierney is younger of course, maybe he can still get better all around.
Tierney is quick. He's a better crosser than Digne. I think he has more about him in terms of leadership, versatility and character.
But, Digne is a decent passer, gets up and down and has experience at top clubs and with France. Questions over his resilience perhaps, if things aren't going his way.
I'd rather sign Tierney at £25m, but if Celtic are wanting loads (like £35m plus) and Digne is available for £10-15m, then it's a smart move to go for Digne.