I mostly use I'm autistic and have ADHD, because there isn't an established term for the property of being someone with ADHD yet.
I know about terms like "kinetic" or "pelagic", but I don't want to call myself something that I then always either have to explain, or risk people completely misunderstanding what I even said.
Another reason is, that saying "I'm ADHD" feels comparable to saying "I'm ASD", like I'm just identifying with a disorder.