From the Chicago Manual of Style:
Compare. To “compare with” is to discern both similarities and differences between things. To “compare to” is to note primarily similarities between things.
The Chicago Manual of Style, 15th edition, p206
It is time to constantly remind myself of English and grammar.
- Chicago Manual Of Style Guide Changes Grammar Rules (huffingtonpost.com)
- The Chicago Manual of Style: The New, the Old, the Free (papercuts.blogs.nytimes.com)