Envelope Detector or Coherent detection in Software

Which is better to implement in Software?
Am demodulation scheme

That would depend upon the application requirements. There's no single answer to such a vague question.

There are no strict requirements,I know that envelope detector is more susceptible to distortion and is insensitive but most of arise from the fact that it uses passive components,which won't be in an SDR.On the other hand Coherent detection offers more efficiency but how bad is it to implement in an SDR?