Babar, by some distance, after that may be Haris, Asad isn't bad either with his driving range. At one point, old Umar Akmal had by far the best technique, but he has gone to cow corner these days, and his technique might be handy in T10 & Sixer's leagues.
Most people consider defensive batting as good technique, which is absolutely wrong. Good technique is the ability to hit a ball on merit, into gap and sort out good balls to defend solidly - and then repeat this monotonous job for hours, sessions, days together with cent percent perfection. Otherwise, we'll have to say Azhar Ali has the best technique and he planned to bat out 16 overs to reach 16 for his good technique (without trying to win it with 2-3 shots).