>> In IDOC there is no error handling facility and it is
used for small data load as the data load performance for
larger data is not good when compared to PSA and it is
mostly used for hierarchy loading.

>> IDOC method is very slow and data is not staged and
cannot be edited.
PSA method is faster, staging is possible,editing is
possible and is the most widely used.

idoc will not support error handling and psa will support 
the error handling.And while you are loading the hirarchial 
data the psa will not APPEAR THE I DOC WILL BE THE DEFAULT.