I don't think I have ever even seen a Moutain Horned Dragon so I can't offer any comparisons to beardies for you. What I can tell you is that I have had my baby beardie for two and a half months now. Right now he is living in a 20 gallon long tank, but within another six-eight months or so I am going to upgrade him to his adult sized enclosure. I am by no means an expert on their care, most of my info comes from some forum surfing and a book I purcahsed, but I have heard a good size for an adult enclosure is 4 feet by 2 feet by 2 feet, so they can take up a lot of space. My beardie tolerates being handled very well and is increasingly calm, though he still has a tendency to sit very still for a while only to try and zoom off in another direction if something moves too fast. I have 3 ball pythons as well, and, though I love my snakes, Yoshi is by far more fun to watch on a general basis. If you chose to get a beardie, make sure the one you purchase is lively and alert, and doesn't spend a whole lot of time laying on the floor of the cage without sitting up, and that his vent area is clean. Also, it helps if they are over 8 inches long when you buy them, since before that they are too fragile to handle a whole lot. I would say my bearded dragon is a very fun pet to have, but at the same time he takes up a lot more of my time than my snakes, since he has to be offered calcium dusted crickets 2-3 times a day in addition to having a salad of greens avaiable at all times. If you are looking for more info on bearded dragons, then www.beardeddragon.org is another great resource!