"Compare With" Or "Compare To"?
In general terms, either preposition is correct, but the choice depends partly on meaning and partly on grammar. In addition, American English generally prefers to when there is a choice, whereas in British English the two different constructions are more evenly spread.
Let’s look first at the meaning of each phrase. To compare can be defined broadly as "to estimate the similarity or difference between things." For example:
Individual schools compared their facilities with those of others in the area.
It is difficult to compare our results to studies conducted in the United States.
In this meaning, either preposition can be used.
However, when compare is used to say that one thing resembles another, or to make an analogy between two different things, to is obligatory:
Her novel was compared to the work of Daniel Defoe.
He compared children to young trees, both still growing and able to be shaped.
A Shakespearean example
One of the most famous lines in English poetry, from Shakespeare’s Sonnet 18, uses compare to in this way:
Shall I compare thee to a summer’s day?
British English prefers with when compare is used intransitively, because similarities are being evaluated:
His achievements do not compare with those of A. J. Ayer.
No other English painter can compare with Sutherland in the subtlety of his vision.
In American English, however, compare to is possible and slightly more frequent:
None of those birds compare to L.A. pigeons.
No, today’s calamities don't compare to the Great Depression or even to the agricultural troubles of the 1980s.
Compared to ...
This was a modest sum compared to what other people spent.
Compared to physics and astronomy, cosmology is a young science.
However, compared with the USA and Japan, Europe contains a group of separate nation states.
Comparable is used with to or with in line with the previous discussion, with a marked preference in current usage for to:
We find ourselves in a situation comparable to mediaeval times.
Social mobility is, in fact, comparable with most countries in Europe.
Comparison as the noun equivalent of compare can be followed by either with or to:
Poussin’s approach bears closest comparison to Michelangelo’s.
Prices for real estate in Tbilisi cannot stand comparison with Western capitals or indeed Moscow.
The phrase in comparison to is more often used than in comparison with, but by comparison with is more frequent than by comparison to:
The film is utterly benign in comparison to some of the more violent movies of today.
The standard is pitiable in comparison with other countries.
By comparison with North Sea oil production, it is a drop in the ocean.
Essentially, both with and to are correct prepositions to use after compare, comparable, or comparison, although it may be worth checking the regional and grammatical context of the sentence when making your choice.
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