2 WordPress sites with same domain

I have a WordPress site https://www.tryhypnosisnow.com with W3 Total Cache active, and I created another wordpress site https://www.tryhypnosisnow.com/hypnosis-downloads/ (I believe this is a subdirectory, if I understand the termninology) where W3 Total Cache is deactivated. Would I benefit from enabling W3 Total Cache on both sites, or would the difference be negligible?