Subdomains and branding

Hi guys,

Our company has 3 different sub-brands and we are wondering what the best practice would be to host our site with the following options:

Have each brand as a separate project and point to a different subdomain:

OR

Have the entire site as one single project and sort them out via URL paths:

Keeping in mind that each sub-brand will most likely have a unique style guide, but also retain some aspect of the overall brand