^another case of OCD. The truth is, choice is limited to what your nearest cobbler uses. My cobbler uses "Powersole", unknown brand to me but it features a slightly thicker toe tap unlike the Vibram or Topies from the pictures.
IMO sole quality should be the least of my worries, because there aren't much raw material choices for "rubber" soles. The glue-job is my primary concern.
Rubber soles can be made soft or hard, so it depends what you're looking for. PU is currently being marketed as a superior alternative. The shittiest choice would be recycled rubber, I think some1 had a nasty surprise