Session is based on nodes that stack a shitcoin, it is not sustainable over time, and setting up a Session node is not accessible to everyone.
Session works poorly.
Session has a unique identifier where it can trace you.
SimpleX is not a blockchain, so it works very well. It also has audio and encrypted calls.
It is decentralized and you can set up your own server in 5 minutes.
SimpleX has no traceable ids.