I'd be ok with both candidates releasing everything.

Let's say Hillary releases all:
Transcripts of bank speeches
Medical records
Meetings with Clinton Foundation donors
Any unreleased still avail emails from private server.

Trump releases:
All medical records with his voodoo gastroenterologist.
All tax returns from last twenty years.
All phone conversation transcripts or dates of meetings or phone calls with foreign governments.

Yes, Hillary might be releasing some embarrassing and possibly damaging information.
But, I'd bet anything that Trumps information would be disqualifying not just embarrassing.

IMHO, it is worth her calling his bluff if he insists on all her medical records.