Certification JAR/FAR 27/29??

[Vertolot]

What is the major differencies between a Normal Category JAR/FAR 27 and a Airline Transport Category Rotorcraft JAR/FAR 29 Certification? How will these certification standards affect Flight Safety and are the certification standards for Category A the same? How should you compare a Normal Category Helicopter to a Airline Transport Category Helicopter in terms of Flight Safety (regarding to the choise of helicopter) for example for an aircaft in the HEMS role?

Thanks in advance