Starters are preferred over direct pitching of a smack pack of vial. You will have a higher yeast count than in the original package. Bear in mind, you really have no control over how that yeast has been handled between the manufacturing plant and your refrigerator. Was it shipped to your LHBS in a refrigerated state? Did the LHBS (or online supplier) immediately transfer it to their refrigerator, or did it sit out on the floor for a day or two? How did it get to you? If you bought your yeast online, it may have sat in the back of a hot truck overnight, or on your front porch for several hours.
Also, even under the best of conditions, it is questionable whether those packages have a sufficient yeast count for any but the smallest beers.