Currently, Pt is in fact 2 minutes easier to speedrun. Such a small difference is likely caused by many minor changes between DP and Pt, so it's difficult to explain.
Getting Battle Tower streaks and competitive battling are definitely easier in Pt. The main reason is that Pt has more move tutors, so more Pokemon can learn strong moves like ice punch or superpower.
There are also a few good Pokemon, like Gliscor and Zapdos, that are obtainable in Pt but not DP.
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