Which is more important to employers - project management qualification or project management experience?

Project management experience.  Project management qualifications is helpful for a project manager to organize and streamline the project, but project management experience helps PM's to rely on experience and judgement to plan and accomplish goals.

both are needed, but usually it depends on projects scale and the organization type. i.e in small size projects you don't need an experienced PM, in functional organization adopt big projects you will need someone with huge experience in managing projects "generally" no matter his experience in certain field, in projectized organization you definitely need an experienced PM specialized in certain field even with small size projects.