Starc was the better bowler but there are reasons for that. His home ground, advantage of being able to bowl in the night with favourable conditions for bowlers and he had good support from Hazlewood and Bird. Its a well known fact that fast bowlers hunt in pairs and Hazlewood provided that partnership.
But, the fact is, had Amir even gotten 10 wickets in this match, I would still go for Starc for the sole reason of that last well set Asad Shafiq wicket. The way they were moving and how even Yasir Shah was easily playing Bird and co with ease proves that it was a pressure situation and Pakistan had a good chance to take the match but the last spell from Starc was fierce. He ran in and bowled at speeds of late 140's on the fifth day of the test match. And to extract that type of bounce from a 60 over old ball is awesome. Jaffa delivery.