MPEP 1502 sets forth the differences between the requirements for patentability of a utility patent application and a design patent application.
In general terms, a “utility patent” protects the way an article is used and works (35 U.S.C. 101), while a “design patent” protects the way an article looks (35 U.S.C. 171). The ornamental appearance for an article includes its shape/configuration or surface ornamentation applied to the article, or both. Both design and utility patents may be obtained on an article if invention resides both in its utility and ornamental appearance.
As DonQuiKong stated, there are different patentability requirements for the two types of patent applications, thus the patentability of one has no bearing on the patentability of the other. You should provide the examiners of each patent application any prior art cited by the other examiner just to ensure that the duty of disclosure has been met.