I think “neurodivergence” is a better label if the goal is gaining strength in numbers. It fully encompasses autism and autism spectrum related conditions, plus ADHD and others. A lot of people don’t want the label “autistic,” but share experiences with people who do, and would love to offer solidarity as an “inside” rather than “outside” member of the community. We now have “AuDHD spectrum” as a thing, but really, I think optimum numbers might come from including folks who identify as “broadly neurodivergent.”

It also leaves room to start distinguishing/separating out more subtle variants of what we currently umbrella as “autism,” perhaps making it better defined in the future. And I kind of suspect doing this with “less profound” neurodivergencies could help folks with “more profound” (and rarer) cases.

To look at a historical case: Gay Rights didn’t make a lot of headway. But adding lesbians, trans folks, etc. ultimately did a lot of good for that community in the US.