All I know is that it is very old technology available for many years before BAHA and Transear were invented. I am not sure how its performance compares to either BAHA or Transear but historically this technology had low adherence rate for the following reasons:
1) appearance - who likes to walk wired? Is it a hearing aid or a conversation piece? You practically advertise that you need a hearing aid and many people do not like it so much that the prospect of unaided SSD is actually more promising.
2) convenience- you lose your glasses, you lose your hearing aid. What about sunglasses, or different glasses for driving/reading? What if your eyeglasses prescription changes? You also always need your glasses to get hearing aid amplification. What if you don't always wear them? I would ask all of that of the audiologist who recommended that along with why he does not want to try Transear or at least CROSS hearing aid. To get BAHA, you would need to go to ENT because surgery is involved.