I have never been on spiro, so I have no direct comparison, but I started HRT with cyprterone acetate. When my T dropped to zero, my endo cut me back to half. He says in Canada cyproterone is the go to AA, and only prescribes spiro to those who can't afford cypro.
All I know is that it works very well for me, my Dr. has extensive TS experience, and I don't have to pee constantly. My .02 cents