The original AP Calipers on our Z were polished and one of the PO’s had painted them red that combined with years of neglect and stains left them unpolishable. No matter how much polishing the calipers still looked dirty. I opted for the “Almost chrome” Powder coat and it has held up really well.
Front:
Front off the car and in direct light:
Front top:
Rear:
Best of luck with whatever you decide to do.
-Daniel