what's your favorite ground based martial art

For me it's BJJ as it has a shared history with the other Japanese arts that I train in and covers both gi & no-gi

Re-quoting this because I think it's an important point

The only thing that I'd add is that, in my experience, not training in (or at least being exposed to) these "dirty tricks" is quite dangerous. It can result in an approach that is exposed to counters (to Hannibal's point: built on foundational / structured ground movement) using dirty tricks

Kesa is, in my experience, a good example of a position that's relatively exposed to fish hooks etc even by people with only a basic understanding of ground movement