For example, I want to say that a writer has great dramaturgic(al) skills (meaning that he's good at writing original, captivating and powerful stories, able to stir the readers' emotions).

The dictionary gives the same definition for both, that is "relating to the technical aspects of drama". On Google, I found more results with "dramaturgical", but I'd like to know if the two terms can be used interchangeably.

I guess probably the best term to use is "dramatic" skills, as Canadian Yankee suggests. According to dictionaries "histrionic" and "theatrical" have too much to do with acting or stage performances (often in a too melodramatic way). I also thought of "writing skills", but it's too general. Even a person writing a résumé for a job application can have good writing skills, but it's better if he or she leaves dramatic skills aside!