Transformation formula vs. routine

Hi Colleagues,

What is better to use in order to improve the data upload performance ?

Characteristic routine or formula routine ?

To have the quicker data upload from DSO to Cube is it better to write the following characteristic routine.

IF SOURCE_FIELDS-COORDER IS INITIAL.

RESULT = SOURCE_FIELDS-/BIC/ZCOORDER.

ELSE.

RESULT = SOURCE_FIELDS-COORDER.

ENDIF.

Or to use formula features to execute the same logic ?

Characteristic routine vs. Formula ? What is it recommended to use ?

Thanks,