Disorder, or impairment, or disability. Namely because as a multiply disabled dude I've seen too many times when the word 'difference' has really been meaning 'not like the physically disabed' and that's just needlessly dividing disablity rights stuff imo. Also, often can serve to lock people with multiple impairments out of conversations in my personal experience. Yes, the access needs for a person with a stutter are different from a person in a wheelchair - but they both still need access and to split it along difference vs disorder or disability to me just seems like, well why split it? We're all fighting for society to be less shit, might as well do it together.