These aren’t great pictures because the camera is not being held level, hence the paint looks more downhill than he is, and the TB more uphill.
That said, the paint is still croup-high, and has a weak loin (lots of space between the last rib and the point of hip). His stifle is high. I don’t love his shoulder, the upper arm is rather horizontal, and the shoulder seems small and bunchy, his withers low. And his legs are shortish. I see a horse that might be a functional western horse, maybe a comfortable ride and a good mind, but nothing that says “dressage” to me. Basic dressage training would help him, but I can’t see him going very far in the discipline. I wouldn’t expect him to have either of two things people look for in dressage: naturally big and suspended gaits, or the ability to collect easily.
There is also something funky going on with the front feet. Very upright pasterns, but a much lower angle on the hooves. Are they due for a trim?
TB is losing muscle mass as an aging horse, which makes him look a bit sway back. I’d say he has better loin and hips for his build than the Paint, but he might still be croup high. His upper arm is more vertical, which would give him better scope over fences. His neck has lost muscle tone, but I would discount that in regards to basic conformation. The fall of the mane and the lighting make it a bit harder to tell where his neck really ties on, by which I mean where does the neck bone enter the body and connect to the spine, not what do we see in terms of external muscling on the throat or crest. I think it is possible that his neck ties on quite low on the shoulder. However, his stifle is a bit lower than the Paint, so that could help with collection.
As far as the actual slope of the shoulder blade, these two horses seem about the same. However, the TB has a more upright humerous than the Paint. On both of them, I feel that the shoulder is a bit small, but I realize I tend to think this a lot because I have a mare with a massive shoulder.
His feet are also funky, long toes. I would suggest some attention to what your farrier is doing, since both horses seem to have the toes running forward (which is not the same as being overdue for a trim).
Summing up, I’d say the aging TB has the conformation to go along with a previous career as a nice lower-level hunter/jumper. Basic dressage exercises could help him maintain muscle tone as he ages, but he is doing well for a 24 year old TB, since they don’t seem to be the longest-lived horses around. I would not pick him to try to train “up the levels,” however, at his age.
The Paint sound like a good casual riding horse, husband horse, kid’s horse, but he doesn’t have the conformation for Western performance or for English riding, and your description of how he goes confirms that.
If you want to improve on the TB conformation, I’d say look for a horse that has a neck bone that enters the body higher on the shoulder. Look for a horse that doesn’t appear croup-high. Look for a lower stifle. But more importantly, look at how the horse moves at liberty, and under saddle if the rider is not constricting him too much. You want some natural loft and suspension in the trot, and you want the ability to collect, stop, and turn at liberty. You don’t want a standardbred that gives you the most beautiful floating extended trot in the world, then falls on his face when he reaches the paddock fence and has to turn. But you also don’t want a wonderful little reining quarterhorse who could pirouette all day, but has a scampery, flat-footed gait.