ZOHO VS. CONSTANT CONTACT

I am using Zoho as a CRM solution within my area of responsibility and I really like it; however, the company in general uses Constant Contact for e-marketing and I am being challenged as to why I need to use Zoho. An "architectural review" committee is being formed to document the my requirements for using Zoho vs. Constant Contact, and I could use some help. Does anyone have a similar comparison or justification that they could share with me? I will be grateful for any assistance as I do want to continue using Zoho.