Which of these cloud software plays has more upside potential?DocuSign (DOCU 0.47%) and ServiceNow (NOW 1.19%) both simplify and streamline tasks for companies with their cloud-based services. DocuSign is the world's largest provider of e-signature services, while ServiceNow's services help companies organize their unstructured work patterns into automated digital workflows.But over the past three years, DocuSign's stock plunged nearly 70% as ServiceNow's stock rallied by roughly the same amount. Let's see ...