One of the forum members complained about 55's AF speed. So I collected several videos of different youtubers letting their DA* lenses hunt. However, it's definitely
not the best test of AF speed and it's not even the best comparison of lenses hunting, because each one may be on a different body and/or a body with batteries with different charges. 16-50 seems fastest, 50-135 seems slowest, while 300 isn't on the list yet.
Nevertheless, enjoy videos of pretty lenses:
Videos of Lenses Hunting