Technically, any equine (apart from zebras and donkeys) under 14 hands high at the withers is a pony. It’s just that some pony breeds are calledminiature horses, like the American Miniature Horse, because they have features more in line with a scaled down horse. For example, most pony breeds have a larger head to body ratio; miniature horses maintain a more horse-like ratio, making them look “finer” than most ponies.
You are correct to call a miniature horse a pony, just don’t expect all miniature horse owners to let you get away with it!
Service horses have advantages that are important to some subset of blind people that need them:
Some blind people do not want to live with a dog, as they aren’t fans of dogs or don’t want a dog as a pet. When a service dog is out, it’s working and is a “professional.” When they are at home they are more like ordinary pets, but well trained ones. Not everyone wants to take care of a pet dog.
Some blind people are allergic to dog dander and would have a degraded quality of life if they had to live with a dog or be around a dog all day.
Horses live much longer than dogs, while most seeing eye dog organizations keep you supplied with a new dog every 7-8 years (the working life of the service animal, roughly) for some purposes you feel better with the same animal for a longer period of time.
There are disadvantages, of course:
Service horses, despite being miniature horses, are still horses. They can’t live in an apartment and need a place to graze and such when they aren’t working. They make special shoes for them that allows them to be inside homes and buildings without their hooves damaging things, but these are grazing animals and need to live somewhere with barn/pasture space.
Some people obviously don’t want a horse just like they might not want a dog or vice versa.
Some people are allergic to horses.
The track record of service horses is much shorter, the program didn’t start until the late 90s. There are fears that as prey animals a service horse may be more prone to “failures” in public that could be disastrous to their human companion.
Dogs can go virtually anywhere people can go: buses, stores, cabs, etc. A horse simply cannot ride in a cab, and there may not be adequate space for one in many other forms of public transportation.
The ADA preempts any local animal laws. This is something I’m aware of through work because we can prohibit pets for example on a lease, and residents aren’t allowed to have pit bulls in a few areas we rent units because of municipal bans or insurance issues but none of that applies to a service animal. Where Federal and State & Local laws intersect the supremacy clause typically guarantees Federal law wins out. The only place I believe you could prohibit a service animal is:
Religious organizations that have religious objections to the animal, but this only protects the religious parts of their organization. Non-religious services or such that the organization provides are governed by the same rules as other public accommodations.
Any place that is not a public accommodation.
A private office closed to the public would still be required to allow service dogs in most circumstances for their employees due to rules on workplace accommodations of disabilities.
If a service animal becomes dangerous or disruptive you always have the option to eject them and the owner, but you better be certain you can prove it later because kicking someone out of a business improperly for having a service animal is actually a criminal offense. A clothing store owner kicked a young girl and her service dog out because he didn’t want a dog near his clothing. When he was charged and realized he was actually facing something like 15-20 days imprisonment and a substantial fine his public attitude of “it’s my store and I have the right to kick people out” very quickly changed to extreme contrition.
Muslims consider dogs unclean, so may prefer a horse.
Speaking of which, there have been issues with Muslim cabdrivers not wanting to pick up fares with seeing eye dogs.
Finally, my experience with “emotional support dogs” is that they are greasy haired, smelly, yapyy, untrained dogs that some crazy middle-aged woman decides she needs.
No doubt there are legitimately trained emotional support dogs that are performing a real service. I just haven’t run into one yet (or it was just another well trained dog in a harness that I assumed was for some other purpose).