For me, the rarest audio drama I’ve ever listened to is RJ01511958. The theme was completely new to me. Personally, it was a bit uncomfortable to listen to at first because (⊙_☉) it's about baby care or adult bb, but I really liked the voice actor performance (⌒_⌒;)
Honestly, it heavily depends on the vibe of the character, but if I absolutely have to choose, I am Team Deep Voice all the way.
There is just something that love about a low and smooth.