Best way to combine two similar document
Your description could corresponds to the NLP task of summarization. This is an active field of research: https://scholar.google.com/scholar?q=text+summarization

A much simpler option is to only extract sentences from both: in this case the goal is not to produce a text which reads like a story, just an enumeration of sentences.

Even in this case you will have to define how to measure "information value", this is not easy afaik.