Hi Joshua,
Do you know if there is any "official" document that may detail that point ?
I'm currently VCP-DCV and preparing for VCP-Cloud. I first started to work with vCloud 5.1 (already followed vCloud ICM 5.1 course) and was preparing IaaS Exam, based on the official training path this was somewhat obvious 
).
Anyway, would you recommand trying Iaas Exam (VCPVCD510) or Cloud Exam (VCPC510), as VCP-DCV and had followed vCloud ICM 5.1 (not 1.5 
) ?
Regards,