Instead of considering the harm in keeping both characters, consider what you stand to lose in cutting a character. It may seem like the same issue, but the shift in thinking is bound to give the story—and the second friend’s inclusion—a much closer scrutiny.

If one character is cut, do you lose anything that’s essential to telling this story? Can the other friend serve the purpose of both? Characters should be distinct and they must also be necessary to the story.

Don’t think of this from the standpoint of the writer’s work. In cutting a character, you may create some significant extra work. For one thing, you’ll have to reconsider every scene in which that character appears. Instead, look at this from your reader’s standpoint. You’re asking the reader to engage with both these characters. You’re characterizing them to the extent that they’re similar and distinct from one another. By giving them attention on the page, they’re gaining emotional weight. You’re creating expectations for the reader. Does the story follow through on those expectations?

I don’t mean to imply that all situations like this need a generous trimming. But really put both characters to the test before making your decision. You want to cut all the fat in your manuscript. Though removing a character makes that task more difficult, your story will be stronger as a result.