The crimes are somewhat similar in that they deal with the death of a young woman at the hands of the boys. But the handling of the crimes by their respective guardian mothers is very different.
Mother features a rather crazy mother who is fiercely protective of her mentally unstable son. To the point that when he unwittingly kills a young woman she does everything in her power to get him released from jail and then cover up the crime. The film is a dark comedy/ drama that remains unsettling and unpredictable in every scene.
Poetry is very different in that it is a grandmother who is caring for her grandson who it turns out is part of a gang that rapes a young woman who then commits suicide. The story is more about the way the grandmother deals with her early stages of Alzheimers all the while trying to write a poem that expresses how she feels. But the issue of her grandson fits into the whole piece in that she wants to do the right thing before she is no longer able to. By the end she refuses to protect her grandson from police detectives even though there is pressure for her to do so by the fathers of the other boys involved in the crime.
Both are very good films and worth seeing if you can. Mother is available on DVD and Blu-ray. Poetry will be released next year in the US by Kino International.