Comparision between Openmrs,OpenEMR,OpenHR.Why some one choose the Openmrs why not the other opensource platform.Looking for a key differences.

I think he got little bit knowledge.He is looking to build a complete solution for Dental management system. He asked me for a module for dental management,I looked for it.I am not able to find any working module for dental management.

So the basic question in his mind is

Question:How openMrs benefits us if we build a dental module on top of openMRS.Why not to choose the openEMR and openHR?