Great Question! As I'm sure many other SEO's here have mentioned.. you should absolutely be leveraging the sub-folder as opposed to the sub-domain as Google and Bing associate sub domains as separate entities with their own value metrics outside of the primary root.

The only real time I would recommend a sub-domain over a sub-directory would be due to platform restrictions (Shopify, Wix, etc) where you don't have access to build an infrastructure to support nested content from multiple hosts.

Definitely worth chatting about, however you shouldn't have any problems using the sub folder with any other host you'd like.