Cat A Vs Cat B
It is my understanding that:
Cat A procedures, if followed, guarantee for either continued safe flight or a safe landing at the point of takeoff or landing should the critical engine fail. This takes into account aircraft performance and the size and elevation the helipad.
Cat B procedures provide for minimum exposure to critical flight regimes during takeoff and landing. This also includes planning for a safe landing area in the mediate vicinity of the takeoff/landing spot should a loss of power be experienced. This procedure typically pertains to single engine machines but can be applicable to multi-engine aircraft that do not have the ability for continued flight after sustaining a loss of one engine. i.e. S-76A operating in Denver, CO