Referring to the 36 core biopsy, since everyone insists on its benefits -
Obviously fewer cores sample less area, and if there is question, a saturation biopsy gives more chance of finding something.
Downside is that many major (U.S.) insurance companies (according to my recent experience and comments from my uro/surgeon, who deals with most major companies) pay for only 6 cores. I was fortunate in that my uro uses Bostwick, and they wrote off the "extra" 6 that my insurance refused as "excessive" after I begged a bit.
I've mentioned before that if only 6 cores had been taken per the approved scheme, I would have still had a positive core, but would have gotten a G 3+4 at the worst. My real biopsy results were much worse. Had I done what insurance would pay for, I would have chosen less aggressive treatment, and would have missed the fact that there was EPE.
I learned at that point that checking for pre-certification and understanding the vagaries of your coverage at each step will reduce the "excessive" stress of having hours of calls with billing departments and debt collectors even before you can think about what comes next. I've been there and done that - although only after learning the hard way. An extra letter from the doctor would have avoided many problems.