How long will you live? If you plan on living a long time - wait.
If you are obese, you smoke and drink, have a poor family history, and are generally not in good health now? Take Social Security as soon as possible.
I am waiting until 70 (66 and about to retire now) because:
—Both my parents are still alive (excellent genes)
—I am in excellent health and good shape
—I make a lot more than my wife so I want to maximize her benefits, particularly if I die first
—I can afford to do it and still cover expenses.
Your mileage may vary..
Which reminds me of this: Do you want to make God laugh? Tell Him your plans.