With larger communities it generally gets harder to keep an overview over the topics and i find it harder to discover new topics and posts. This is of course my personal opinion. For smaller communities though i really like the discourse model and would choose this every time if it was for a smaller community.
It is getting better and better though so maybe in 1-2 years it would be top notch for larger communities too. I do not know, BUT i know that the discourse team are doing a fantastic job so properly 🙂