Ah yes, Kanté. I'll have them both in my midfield in my EPL team of the season. Still, I'll have to go with Dembélé since his all round game is much better and is capable of dominating the midfield unlike Kanté whose strength lies more in winning the ball.
Dembele is strong and a good dribbler but lacks the true attributes of a top CM IMO. Not decisive enough, doesn't create or score nearly enough. Range of passing is average, positionally can be suspect too.
Dier and Dembele is never in a million years a title winning duo. I like Dier too.