Compared to, or compared with?

I have never really known the difference between the phrases "compared to" and "compared with", and frankly it hardly even matters. Both constructions are grammatically correct, and in most instances either will do nicely, as the sense is usually pretty clear.

It's only when we get into more subtle areas of meaning that the distinction between the two becomes (slightly) important. And, if you look for advice on the Internet, you will find some confusion and inconsistency.

Many people would argue that the most commonly-accepted wisdom is that "compared with" should be used when comparing two things that are of essentially the same type or classification, while "compared to" should be used for two items of essentially different characteristics. So, use "with" to stress similarities (i.e. where the similarities are more important than the differences), and "to" to stress differences. For example:

"Her cover songs were favourably compared with the originals."

"He compared her eyes to the deaths of the ocean."

This is the conclusion to be found on websites like Grammarist (which I trust for most purposes), Difference Between, Experts Global, LetPub, Pediaa, MyEnglishTeacher, American Heritage Dictionary, etc. 

However, quite the OPPOSITE opinion - that "compared to" stresses differences or juxtaposes different types of things - is to be found in several other sources, like Lexico, Writing Explained, Writing Skills, HiNative, JForrest English, Doris&Bertie, etc. So, there is clearly no consensus.

Daily Writing Tips quotes advice from various different authorities, and even here there is some confusion: Strunk and White's Elements of Style avers that "with" suggests similarities and "to" suggests differences, but the Penguin Writers' Manual and the AP Stylebook both say the opposite. 

This StackExchange conversation shows a similar level of confusion and contradiction. It also quotes from Garner's influential Modern American Usage, which suggests that "with" should be the default preposition, and that it should be used to place two items side by side, noting both the differences and similarities between them, while "to" should only be used to point out likenesses between two things. 

EnglishForums.com quotes the equally influential Fowler's Modern English Usage as preferring "compared to" to suggest a similarity, and "compared with" to suggest a supposed or spurious similarity. The extract from Fowler also gives the enlightening examples of, "He compared me to Demosthenes" (suggesting a positive comparison) and "He compared me with Demosthenes" (suggesting a less favourable comparison). Subtle indeed.

GrammarBook manages to come up with a different distinction entirely, suggesting that "compared to" should be used when expressing an opinion or making a personal observation, while "compared with" should be reserved for occasions when the writer is looking to make an impartial or empirical comparison, which seems like a particularly fraught path to pursue.

Just for interest, a Google Ngram of the relative frequency of use of "compare to" and "compare with" shows a distinct historical preference for "compare with", but with a sharp reversal in the trend starting in the latter half of the 20th century, to the extent that "compared to" looks like it will be the more popular phrase in the 21st century (looking at an Ngam of "compared to" and "compared with", that cross-over has already occurred).

As you can see, then, there is much contentiousness and no consensus. Me, I would still go with "to" to compare different classes of things, and "with" to compare similar things. After all, Shakespeare didn't write, "Shall I compared thee with a summer's day" (and we should be glad of that!) The bottom line, though, is that it doesn't really matter.