Well, I seriously doubt that what is being sold as 'ox tail' in markets actually comes from an ox. I'm sure it comes from the same steers as all the other beef but it does sound odd to say, "steer tail," or even "beef tail." Obviously, it is one of those (pardon the expression) 'odds and ends' items and as such one might think it to be fairly inexpensive. This is not the case however, as it is sold at a premium price competing with other choice cuts. Clearly, there is good demand for oxtail.
For beef stock meat, oxtail is clearly the best by far. When cooking in large batches I'll use bone and sinew, but for smaller pots oxtail is the meat of choice. It takes a full three hours to soften, with conventional stockpot additions. Clove-studded onion is de rigueur. The best thing of all about an oxtail stock is that it requires no further handling; it ready to ladle into bowls without any training or modification.
I treat oxtail as luxury meat. I know of oxtail stew and other such dishes, but I would never modify its liquor unless I had many pounds of on hand. I also never use it in any heavily flavored soups. I've had the best luck with oxtail soup using carrots, celery, parsley and maybe a bit of barley as it's filling, pleasantly chewy, and neutral in flavor. Crusty baguettes go well with oxtail soup, and it may be served with cheese for contrast. Also, exotic salad greens and herbs dressed with a simple vinaigrette are quite nice with the soup.
Heading East to Vietnam, oxtail makes a premium stock for delicious pho. I find the basil and bean sprouts to not be in the least compromising, and the rice noodles work perfectly if you make sure you have a strong starting stock. Use chili sauce with beef strips on the side to avoid ruining the stock.