First, consider the following scenario:
ServiceCompany and ProductCompany are two unrelated single-owner companies selling different solutions to their customers. They decide to help each other and create a parent company named ParentCompany which will be a mutual brand between both child companies.
Both ServiceCompany and ProductCompany will both continue to sell their original solutions, but they will be a part of ParentCompany and refer work to each other as a result.
Now, onto the SEO question:
Which would be most beneficial in terms of SEO? (Let's assume neither of the child companies have an existing website or SEO history.)
Option 1. Create
ParentCompany.com and display information about both child companies (blog about both, provide information and calls-to-action for both, etc.)?
Option 2. Create
ProductCompany.com and individually market their services?
Option 3. Create the subdomains
Product.ParentCompany.com and treat them as different websites.
Ideally, it would be nice to have a Parent website which encompasses all that the child companies offer because of the ability to build and manage a single website to handle both. However, would having two unrelated solutions on a website cause problems or additional obstacles in the SEO process?