Utility patents protect the construction or function of a product, while design patents protect the appearance of a product or a portion of a product.  Because utility patents and design patents each protect different aspects of a product, it is possible, and often desirable, to try to obtain both types of patents on a product.  Each type of patent offers certain advantages:

Advantages of a Utility PatentAdvantages of a Design Patent
Protects the construction or function of the invention, regardless of appearance.Protects the appearance of a product from simulation by competitors
Allows the utility patent applicant to mark the product “Patent Pending.”Allows the design patent applicant to mark the product “Patent Pending.”
Usually has a longer term than a design patent.Usually less expensive to obtain than a utility patent.
Usually easier to obtain than a utility patent.
Allows the design patent owner to recover the infringer’s profits, in addition to other remedies for infringement.
Comparison of Utility Patent and Design Patent

Where only appearance is important, a design patent may offer sufficient protection. Where the construction or function of the product is important, a utility patent may be needed instead of, or in addition to, a design patent in order to adequately protect the invention.