Hey everyone, 
We have a tonne of old domains we have done nothing with. All of them are keyword-rich domains.
Things like "[City]SEOPro" or "[City]DigitalMarketing" where [city] is a city that we are already targeting services in.   So all of these domains will be targeted for local cities as keywords. We have been having an internal debate about whether or not we should just host sales funnel pages on these domains, that are rich in keywords and content......... ... Or ... ... Should we point these domains to landing pages on our existing domain that are basically the same as what we would do with the sales funnel pages, but are on our primary site? (keyword rich, with good and plentiful content) Then, as a follow-up question... Should these be set as just 301 redirects on these domains to our actual primary domain so the browser sees the landing page domain instead of the actual keyword-rich domain? ( [city]seopro.com ) Thanks guys. I know for some, the response will be an obvious one. However; we have probably way over thought this and have arguments for almost every scenario. We think we have an answer but wanted to send this out to the community first. I won't post what we are thinking yet, so that the answers can remain unbiased for now and we can have a conversation without it being swayed any one way. We understand that 301 redirects would be seen as a doorway page. 
We are also only discussing in the context of organic search only. 
If we ran the domains as their own sites, they would be about 3 pages of content only. Pretty static, but good content. Think of a PAS style sales funnel. Problem -> Acknowledgement -> Solution.