Has autism or is autistic

People say a lot about whether the correct term to use is "they have autism" or "they are autistic." Some say that "they have autism" is incorrect because they do not lug around autism like a hiking backpack full of rocks. After all, when was the last time you heard "she has womanliness" instead of "she's a woman"? Autism is often such a huge part of an individual's personality that they feel it wrong to refer to that part like you would a suitcase.
On the other hand, saying "they are autistic" still isn't right for some people. The word autism has a lot of negative connotations with many people, and very few people want these to follow them like a label everywhere they go. Then there's also the fact that no individual is just a big walking ball of autism with nothing more to them. Personally, I've always felt that calling someone autistic is a bit like ignoring all non-autistic parts of them in favor of an easy label.
As for which is superior, I don't think either term is perfect. There's always someone who will feel offended by either term. I use the "they have autism" way of saying it to try and avoid slapping a label on anyone who has autism/is autistic, but I worry that I'm still offending people.
To put it simply, you can't win. The saying goes that "you can't please all the people all of the time," and it's true. You just have to either use the term you favor or find out the preferred term of who you're talking to.