Those who till the flinty soil of grammar and usage often pause, wipe the sweat from their brows, and ask, “Should this be compared to or compared with?”
The sibylline advice of the Associated Press Stylebook, memorized by generations of copy editing acolytes, is to use compare to for indicating similarities and compare with for “juxtaposing two or more items to indicate similarities and/or differences.”
How many similarities and/or differences can be juxtaposed on the head of a pin?
One feels an uneasy kinship with the late James J, Kilpatrick, quoted in Merriam-Webster’s Dictionary of English Usage as saying, “I will never in my life comprehend the distinction between compared to and compared with.”
And in actual usage, as described in MWDEU, the distinction is neither neat nor clear-cut.
What is clear-cut to MWDEU is that the active verb is almost always used with to, as in Shakespeare’s “Shall I compare thee to a summer’s day?” But when it comes to participles, compared to and compared with tend to slide either way.
Jeremy Butterfield points out in his edition of Fowler’s that in the sense of weighing and balancing one thing against another, U.S. usage favors to while British usage is mixed. And when the participial form precedes a dependent clause, “usage seems to be moving in favour of to.” Viz.: This is a modest rule of thumb compared to how the AP leads you to verbal gymnastics.
In any event, you civilians, heretofore, and blissfully, unaware of these intricacies, may continue to write as you have been, and the rapidly dwindling cohort of adepts in journalism can ponder whether the game is worth the candle.