Fairly recently, someone asked me which of these forms is correct. The answer is that they both are. They mean different things, though, so I thought I’d take a look at how they should be used properly.
‘Compare to’ is used in the context of likening something to something else. ‘Compare with’ is used in the sense of evaluating them against one another.
Thus, if I write an article about the two great Argentinian number tens of different eras and say, “In my piece, I compared Lionel Messi to Diego Maradona,” I suggested that they are similar. On the other hand, if I write, “In my piece, I compared Lionel Messi with Diego Maradona,” it means that I made a comparison, assessing their respective merits.
Perhaps a good way to remember the difference is to call to mind the opening of one of the most famous pieces of poetry in English – Shakespeare’s Sonnet 18. “Shall I compare thee to a summer's day?” asks the poet in the first line. Here, he uses ‘compare to’ absolutely correctly: he’s likening his beloved to a summer’s day, no doubt invoking associations with brightness, warmth and so on.
He then goes on to list all kinds of ways in which his beloved is superior to a summer’s day. For instance, it is short, whereas his beloved’s beauty is long-lasting. Thus he’s comparing her WITH summer, and finding that she comes out on top.
Below is the full text for readers to enjoy.
Sonnet 18
by William Shakespeare (1564-1616)
Shall I compare thee to a summer's day?
Thou art more lovely and more temperate.
Rough winds do shake the darling buds of May,
And summer's lease hath all too short a date.
Sometime too hot the eye of heaven shines,
And often is his gold complexion dimm'd;
And every fair from fair sometime declines,
By chance or nature's changing course untrimm'd;
But thy eternal summer shall not fade
Nor lose possession of that fair thou ow'st;
Nor shall Death brag thou wander'st in his shade,
When in eternal lines to time thou grow'st:
So long as men can breathe or eyes can see,
So long lives this, and this gives life to thee.
