To compare subjects is to draw attention to their similarities, although the word compare also has a broader meaning that includes a consideration of differences. To contrast is to focus only on differences.

Whether a paragraph stresses similarities or differences, it may be patterned in one of two ways. The two subjects may be presented one at a time, as in the following paragraph of contrast.

SUBJECT BY SUBJECT

So Grant and Lee were in complete contrast, representing two diametrically opposed elements in American life. Grant was the modern man emerging; beyond him, ready to come on the stage, was the great age of steel and machinery, of crowded cities and a restless, burgeoning vitality. Lee might have ridden down from the old age of chivalry, lance in hand, silken banner fluttering over his head. Each man was the perfect champion of his cause, drawing both his strengths and his weaknesses from the people he led.

—Bruce Catton, “Grant and Lee: A Study in Contrasts”

Or the paragraph may proceed point by point, treating two subjects together, one aspect at a time.

POINT BY POINT

Two men, two speeches. The men, both lawyers, both from Illinois, were seeking the presidency, despite what seemed their crippling connection with extremists. Each was young by modern standards for a president. Abraham Lincoln had turned fifty-one just five days before delivering his speech. Barack Obama was forty-six when he gave his. Their political experience was mainly provincial, in the Illinois legislature for both of them, and they had received little exposure at the national level—two years in the House of Representatives for Lincoln, four years in the Senate for Obama. Yet each was seeking his party’s nomination against a New York senator of longer standing and greater prior reputation—Lincoln against Senator William Seward, Obama against Senator Hillary Clinton. They were both known for having opposed an initially popular war—Lincoln against President Polk’s Mexican War, raised on the basis of a fictitious provocation; Obama against President Bush’s Iraq War, launched on false claims that Saddam Hussein possessed WMDs [weapons of mass destruction] and had made an alliance with Osama bin Laden.

—Garry Wills, “Two Speeches on Race”