My understanding is that Synapse (the current matrix.org server and most common+complete server implementation) performs perfectly adequately unless you are an absolutely huge server (which is basically just matrix.org). They are making performance improvements to Synapse but it is an ever growing battle.

Running your own server to switching to a smaller host will likely get you much better performance without needing to switch away from Synapse.

I don’t know if they have done the same type of performance testing for Dendrite, but hopefully it will be good one day.