Home Alkaline Phospatase (AP) or Peroxidase (HRP)? Which is the most sensitive?

NBT/BCIP substrate for AP is the most sensitive but, not widely used because the reaction is slow, does not allow adequate nuclear counterstain, the signal can diffuse and is not compatible with permanent mounting media. Development using DAB substrate for HRP is far more common due to speed of reaction, precise deposition and acceptable color contrast with nuclear stains.