I'm currently using tiddlywiki[2] so that's primarily what I'm comparing it too.
Both tiddlywiki and dendron look very similar, supporting various forms of linking to one another. Dendron seems to have a more complete hierarchical way of combining pages, at least compared to the way that I use tiddlywiki.
Tiddlywiki's advantage is the amount of plugins it has available. I think I also still prefer tiddlywiki because I just have it hosted on a server, so I can access my notes from whatever machine, including my phone. For dendron ( an electron app ) I'm guessing I would have to have some sort of Dropbox/Nextcloud system setup to sync notes between machines. The fact that I'm in my browser all the time and can just open a web page to access tiddlywiki is also preferable. The least amount of friction between a thought in my head to being able to write it down, the better.
I was interested in Dendron because looking at its website, dendron supports a graph visualization of all your notes, like concept mapping[3]. But unfortunately it doesn't look like this concept mapping feature is prioritized, or the main focus of dendron. That's really the main thing I would like to add to tiddlywiki, some sort of functional concept mapping feature. I've tried tiddlymap[4], but its not very well supported.
[1] https://www.youtube.com/watch?v=3io2fHRmZsE