Hi Jessica — I actually gave a talk at CSUN in March with David Fazio on this very topic (doing UX with PwDs). There are a number of important considerations for that type of research, not the least of which is you can’t do A/B testing on paper with people who are blind. You need to have an app/website that is at least nominally switch and screen reader accessible to ask PwDs “OK, how can I improve this?”
If you are asking me which is MORE important, I probably think employing PwDs is the more important of the two (with the understanding that this is like asking a mother which child is their favorite). When you have an employee with a disability, they will be able to provide continuous input and be a force behind making the company in general more accessible. Also having a person with a disability moderating the UX research typically gets better results since the participants are more likely to open up to someone similarly situated, even if the disabilities are completely different.