You haven't said what you want to do with the horse, your experience, how you keep your horses. That makes a big difference. Competitive trail riding and putting in hours a day at speed? Working on a ranch several hours a day all year? Wanting to go to the World Equestrian Games and win the Individual reining? Or like most people, a companion and friend for the occasional trail ride and a few local shows a year...but not too hot about whether we win or not, just going for fun.
Going to write as if you're a 'typical rider' - love horses, has some experience, not a lot of formal instruction, wanting a nice, sensible family horse, and wanting to ride on trails near home now and again, and ride around your pasture most of the time, take the winter off, and maybe show a little locally at 1-2 shows a year - showmanship, western pleasure, at saddle club and community type shows.
Most of the pictures show horses that are under-muscled and under weight. I'm guessing maybe the Appy mare is the only one that's fed up well and looks like it has had any work any time recently, IF that picture is recent. Don't get fooled by older pictures when the horse was in a summer coat and had a bath.
I'd more expect her to look like the rest of them when you go to see them, though sometimes people have one or two they keep up better.
Forget anything the seller says except breed, age and height, and take that with a grain of salt. Pay no attention to anything about reasons for sale, and pay little attention to stories of what the horse has done unless you can look it up on say the USEF website and verify it. I cannot say how many times I have heard sellers say 'I had a baby' or 'I don't have time for them all' and my friend would take one home and wonders of wonders it was lame. GEE. Don't let this be about what the seller says, forget that. Look at what the horse is now in front of your face.
Horses tell you who they are. Loud and clear. How they move around you, how they listen to you, how they react to traffic, odd things around their home, and how they act when saddled, bridled, brushed, led. The sore horse acts sore. The untrained horse acts untrained. The drugged, tired out horse acts that way.
Pictures of being rode? I could care less. I already know a crazy or untrained horse can be worked to death before the parade or that it might have been from years ago before he went nuts, went lame or got neglected for four years.
I am leery of anything that is not in work, and I don't care what the good sounding excuse is for why. I'm better off looking at fit in use horses. If I want a trail horse I want to see it on a trail ride - TODAY. I would not look at anything unless it got worked steadily over this summer unless I felt like playing Russian Roulette and could afford to support a pasture pet and another one I can actually ride.
Leave the ones out of work to the professionals and those who can afford to gamble. Yes I have gambled and it took three years of work, work and more work to make up for all the training and handling and medical care and wrong feeding the animal had , and to heal up his feet. He'll never be as sound or as reliable as one that was done right to start with. Sure it comes out great sometimes. Most of the time it don't.
If you are looking for a family horse for casual use, to be a pal for occasional rides, and maybe once in a while go to a little local show, I would not be too much concerned about the 'blemishes' on the older horse. Those are rubs from a blanket or saddle. An hour or less trail ride mostly at a walk three times a week, unless the terrain is very challenging, it is not necessary for the horse to be a perfect specimen, but his legs and feet should be in good shape and serviceable, he should be serviceably sound, and he should be gradually conditioned to do it over months, like any athlete.
Not concerned about a long back not carrying the rider well, unless you really are going to use the horse only for VERY long rides often. I never saw a long backed horse not carry a rider well. Not concerned about the horse with 'high withers', his withers aren't really that high, he's thin and out of shape. There are plenty of used saddles for sale for western horses that are a little narrower and more withery.
So what IS important to the average rider? Temperament, temperament, and temperament. After that, temperament and temperament. For the family horse, 1. temperament. 2. training. 3. sound enough to do what you want to do, with a little room to spare
That said, the one photo of the app, she looks too sharp and quick minded for a family type horse. Go for the horse that does NOT thrill you, that stands quietly for pictures, that is easy to ride, and will stand there on a loose rein til you want to go somewhere.
Buying a horse should be like an arranged marriage, not like falling in love. You will fall in love after you are together and the horse serves you well and takes care of your behind when you need him to.
