We have an animated video on that here:
https://video.simplifiedprivacy.com/simplexsession

Session is more decentralized and designed to resist censorship with blockchain based identity.  SimpleX is federated but without having an identity tied to any server.  So this enables you to have no identity.

SimpleX is better for being invisible.  Session is better for this purpose of uncensored free speech. 

 Yes i think this is why i ultimately went with Simplex after trying both.  The user experience seems smoother with Simplex too as well as message reliability.

So im not really sure where Simplex fails when it comes to censorship resistance?

Great video by the way, thank you! 

 SimpleX uses regular domain names for the SERVER addresses.  Then when you make a link to share, it’s linked to a specific server.  When we say censorship resistant, we’re referring to distributing content without physical locations, which are what domain names are linked to.