We were told in class NOT to do one of Plath's poems...
It's not only about the two sides of the story whole idea, but also the idea of truth itself as a subjective construct. Another Plath poem - such as the one corresponding to Hughes's 'Sam' - only shows Plath's side of the story, whether they match or not, i don't know, but that's beside the point. Plath's poem only shows her perspective, it doesn't really give the reader more info about the truth itself and telling it. Not just in the case of the Hughes-Plath relationship.
I hope I made sense! It's hard to explain it... this whole stupid topic is hard to explain! ah!