If you are talking about the free plans, Incapsula provides a dedicated CDN and bot mitigation. Paid services offer extremely strong security protection (remember, Incapsula started as a security company). Incapsula offers strong DDoS protection (always on protection, with a dedicated network operations center - these aren't features Cloudflare has). With Cloudflare, if your site gets attacked you have to manually turn on protection.
You can see a vendor comparison
here. If you are talking about the free plans, Incapsula provides a dedicated CDN and bot mitigation. Paid services offer extremely strong security protection (remember, Incapsula started as a security company). Incapsula offers strong DDoS protection (always on, with a dedicated network operations center), as well as secondary SSD caching. This is in addition to the other benefits you would expect to get from a CDN. Incapsula's CDN offers dynamic caching, serving cached resources from physical memory, as well as secondary SSD caching. This is in addition to the other benefits you would expect to get from a CDN.