I came across the following question on an internet marketing forum and want to answer it here from personal experience:
Q: Hi, there. I have a website with a niche directory. I am building another directory in a somewhat related niche and I am trying to decide if I should add the new directory to my existing website or build a whole new website for the new directory. Which would be better for SEO and ranking on Google?
By the way, it’s not only a niche directory, I write and post articles related to the niche as well so, it’s more like a resource website built around a niche directory.
A: Build on the existing website.
The reason is mainly due to domain authority and Google trust. If you build up a high quality domain, then Google trusts your website and will send you traffic. You also gain recognition from your visitor and they seek out your website. If you start a new website, then you have a brand new domain that needs time to gain trust.
It’s easy to create subdirectories on a website. Just create a new folder on your web host. For more advanced technique, create a subdomain.
If you want to build a large directory network, then go with separate websites.
However, I think you will be best off using 1 domain for all your needs. Better to focus your efforts than spread yourself too thin.