Why not to delete
This is a general point of view about the tags change/renaming:
there is people that distinguishes among similar answers through the tags
(Similar, not only inside a single stack exchange site).
Moreover it's possible that I remember how to arrive to a question find in the past specifying that tag and some other words meanwhile I don't remember its title. When we delete a tag we go to damage that kind of memory and research.
Let's do them synonym
Said that, I agree that those two tags should be "synonymized".
We can choose one tag, leaving the other with an excerpt that says something similar to:
"Deprecated tag synonym of the_other_tag, please use the_other_tag instead".
file-comparison? That tag has 201 questions and 5 followers (30 new question this year) instead of the other one has only 26 question and 1 follower (3 new question this year). It seems people pick out more easily the first one...
file-comparison, they both describe the same thing and one is too broad, whether or not more users use it. I do think the 'either line by line...' should be appended to the end of the final description. Is
comparisontoo broad to be a topic here? Like comparing Win 7 vs Win 8?