XMPP servers and clients have different standards. Some supports audio/video calls

And the same is true about Matrix lol

Make sure you understand volume block size before you start using it. It has a big impact on compression, performance and even disk utilization. In certain configurations you may be surprised to find out as much as 25% of your disk space (in addition to parity) is effectively gone and it is untrivial to change the block size after the fact.

Trilium for the same reasons, but the featureset of Trilium is more like Obsidian.