The specifics will depend on the nature of the age-related disability...which extremity and which side, right or left. Bad hips or bad knees, I think the 7/9 is easier because you have more options to pull your yourself up with upper body strength IME. In a real pinch (knee or hip post-op), you can put a small folding step down and climb from it to the metal step to the wing. Some attached paracord and you can just pull the step up, fold it, and slide it into the back. I did that for awhile when I was post-op from a tendon repair in my right leg. I haven't fully recovered yet, find it easier to enter my 9A on the right side for the time being. In my particular case I found it very difficult to get into a buddy's RV-12.
Bottom line...age-related entry and exit is a reason to consider a high-wing airplane.