Generally, I can only answer to complex or child-onset PTSD. I don't think I can speak for adult onset PTSD.
Both my H and I appear high functioning and "normal." But when we met, I knew we had something in common that marked us as more sensitive to feelings and in need of healing. It is like we could help each other heal because we were both healing something from childhood. I had grown up in a wealthy, abusive family with lots of education. He grew up in a supportive, working class family without education, and a hard time in school despite high intelligence.
I think I agree with Arfie that having something is a strength or weakness depending on the couple's attitude toward life and self. If we have proactive and matching goals and attitudes, then we can make it work.
PTSD brings a host of issues that test the relationship, like trust issues. It's easier to work through these if the PTSD sufferer is not also afflicted with addictions and a cluster of other disorders or health problems.
I don't think a PTSD sufferer and someone with no emotional trauma living a charmed life would have an easy time understanding each other. But, it seems best if there are strengths that complement each other.