I normally don't like to post about my work, but I'm an occupational therapist. Basically, when it comes to aging and hands, the profession is considered the experts. Now, I say this as not to an appeal to authority, but to at least show my perspective. I also say this as an acute care and rehab general practitioner... not a certified hand specialist.
I'll also add that this is my layman's version that I'm texting out on a cell phone, so I'm going to try and keep it simple. It's amazing how complicated some medical people makes things........
Ok, with that outta the way, "old man hands" is not universal. Everyone ages differently. Common sense, I know. But one thing I find most people focus on is "strength". Honestly, most elderly have decent hand "strength" (grasp and finger flexion). The issue is generally coordination, dexterity, fine motor, whatever terms you wanna use. The fancy word is "ataxic movements". I jokingly call it "drunk hands" to a few patients.
Another issue is the Range of Motion (ROM) of the fingers. Arthritis is the big culprit here, but there are a ton of other reasons why as well. Normally, with most of my patients, thumb, index, and middle fingers (think handwriting or using a spoon in a "tripod" grasp) are the most useful as time goes on, maintaining more ROM than the ring and pinky. It's kinda how the hand just naturally works.
If you're bored, our quick test is called "serial opposition". I'm sure you all have done it before, but touch each finger to your thumb in succession. Pointer to pinky, and then pinky to pointer. Now do it fast. Probably notice your tripod digits are easiest to "oppose".
I find SA revolvers to be a theoretical issue for a generic aging hand. It requires too much coordination for a complex manual of arms, and relies heavily on the whole hand for reloading and shooting.
I think a medium framed 38 special DA/SA with a nice trigger is a good idea. For an aging hand, I think loading speed loaders is harder than loading a cylinder.
I think Smith hit it out of the park with the EZ series. Issues can also be the manual of arms depending on the person.
Depending on hand size, I also think a heavy but loose "thumping" gun like a Ruger P90 that I used to own would be good. As a comparison, if we have a patient with a tremor, the first thing we do is give them weighted silverware for eating. It works quite well to steady the shakes.
So I guess I would say "it depends", and honestly, it might take trial and error.
Oddly enough, a classic "old man" brand in Smith& Wesson seems to have the best options for both DA/SA Revolvers and Autos as a starting point. So I'd look at their catalogue first and see which ones are "easiest for you".
And if S&W wants a practitioner to assist in any testing and reads this for any reason, I'm you're man.