pick the 9am oneProbably doesn't matter but if there are 2 AC slots, one from 9am to 1pm and one from 2pm to 5:30pm, is there any benefit to picking either one over the other?
Top tip (in my opinion) for picking interview timeslots is to find a time when your interviewer is most likely to be friendly, energetic and keen to have a conversation with you. Don't choose Mondays or Fridays. Morning slots, right after they've had their coffees, are better than afternoons (your interviewer probably just wants to go home).