Based on that I do not get why a portmanteau of both words is such a bad insult in English that I will not write it General Questions just in case. Strange language, English is. 
There’s a meme for that. (OK, I just made it.)
I have seen asses put to work like that, and I was very much wondering what millennium it was, and whether I should inform the animal cruelty people.
I’ve seen small horses used for tourist work on the Yucatan side and some of it seems cruel. The donkeys I saw pulling material up narrow roads in PV looked healthy and I wasn’t as concerned about their well-being…much more like the mule work I see in the wilderness areas of Idaho as well as in the Grand Canyon.
A couple of the Grand Canyon mules once got loose from the corral on the rim because of pranking teenagers, and couldn’t be found. They showed up later in the day at Phantom Ranch at the bottom of the Canyon. At first glance it might seem dumb, but maybe not. They wouldn’t be sent down twice in a day. So they might have figured if they wait, somebody will put 200lb on their back as usual and send them down. If they head down right away, it’s a hell of a lot easier.
Mules are commonly used to ride and as pack animals in the mountains here in Panama. I was riding one once down a steep trail from a remote site when it stopped, and then started again suddenly. Because my saddle hadn’t been tightened enough by our mule handler, I fell off and broke four ribs. We were still a long way from a road, so the only thing was to get back on and ride for another couple of hours. Fun times.
From the Grand Canyon Visitor Center website:
Mules are steady and more surefooted than their equine counterparts. Mules are dainty steppers and take small, sure footed steps, a quality that is immensely useful in rough terrains. In addition to small steps, they put their rear feet in exactly the same spot where their front foot had been. This leaves very less room for slipping errors. Mules don’t spook easily. Even if they do, they just stop and refuse to move forward. Horses, on the other hand, when unnerved by terrains or heights tend to buck and gallop away, often losing their footing and throwing their riders off balance. Even if they sense that a path is unsafe, they will venture out and learn things the hard way. Mules are more dependable creatures since they can carry a lot more weight and it is no wonder that they are called the beasts of burden.
In very hot climates, mules are much more useful than horses, both for riding as transportation, or as pack animals. Unlike horses, they drink very little, and can eat thorny plants.
I recall a thread around here in which people in-the-know were discussing the intelligence of farm animals. At least some posters reported knowing horses that were incredibly dumb.
As I recall, when we hiked down the GC, the mule strings that passed us by were led and trailed by mules, not horses.
Are their genetic differences between a hinny and a mule? Or are the differences in the 2 hybrid animals just due to what type of womb they were in?
If the hybrid was xx female, it seems like it can the same genetic combo for a hinny or mule.
I don’t know all the details in this case, but epigenetic factors can include RNA which is only passed down from the mother.
There are small horses trainable like seeing eye dogs (I think for people who are allergic to dogs). I have a hard time seeing horses as unintelligent. Sure, donkeys and mules are even more intelligent, but I think horses are pretty smart for prey animals.
I shall require more photos of Joey. 
Glad you’re ok now (right?) but is there any asshcam footage of the accident?
The right answer is:
You bet your sweet ass!
Why do they use horses/donkeys/mules to haul loads in the first place, though, instead of a ute or pick-up truck?
Why use a truck, instead of an animal?
Where? In Mexico or in the Grand Canyon? In the Grand Canyon the trail is way too narrow; maybe 3 feet wide. Maybe 4. Probably true in Mexico as well, especially trails leading up into the mountains to little villages or houses.
General George Crook preferred mules to horses.
Years ago out at Sabino Canyon we met a friendly woman who was out riding her mule and my father, curious, asked her if she considered mules to be that much better than horses. She replied yes, and she would never ride a horse again as mules were just so much less spookable. The mule was busy nudging me for attention.
I especially mean the mules and donkeys dodging traffic and inhaling exhaust in Puerto Vallarta and even bigger cities, and it’s not limited to Mexico. Those are no mountain trails; if normal cars are able to circulate, I do not get why you need pack animals to pull a trailer in the middle of a city.
Because you can’t afford a pickup truck… and gas?
And you have the animals available and a place to graze them? Maybe you live on a small farm on the outskirts of the city?