Smith is at least twice the batsman than Haris - in T20 that is. Overall stats may be similar, but on AUS condition, it's not even a fair comparison. Most of the PAK player's T20I stats are inflated because of playing against too many "soft" teams with compromised squads - even that didn't help in latest series. You'll notice that, often PAK players has a better T20I stats that T20 stats, because they play inferior opponents in T20I than Franchise games.
Haris-Smith, Amir-Starc, Shadab-Zampa .. these are comparable players only on stats for a reason, but even that's not applicable in Australian condition - add to that the fielding capacity of respective sides, the contest will be one sides. I hope PAK plays better than expected, but apart from Imad and may be firing Irfaaan, no PAK T20 player will make Aussie squad in AUS, not even Babar over their two openers, but might find a spot at 3 pushing Smith down. Haris will cost PAK on those large grounds by converting triples into doubles or doubles into singles - just wait and see.