As seasonings, both soy sauce and miso have the same ancestral roots. That said, nowadays the many variations of miso outnumber those of soy sauce. However at the same time, it could be argued that the actual taste of these different miso variations is in fact less diverse – in other words, that miso is perhaps not as fully developed as other seasonings.
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Try to imagine the sales floor of some shop. In the case of soy sauce, koikuchi, or "strong soy," has been and continues to be the standard, as is thus the most produced and the most commonly stocked by stores. And yet in contrast, if we look to the miso section, there is a vast variety always on offer – this is the key difference.

In the past, both miso and soy sauce would have been homemade, and therefore every family would have their own unique style and taste. However with the advent of industrialization, the soy sauce companies modernized more rapidly than those producing miso, and thus, in order to make production cheaper and more efficient, the product ranges were made smaller, focusing on the most popular varieties. Miso producers, in contrast, had, even as early as the Edo Period, implemented a system relying on small, local producers. This allowed the preservation of a multitude of regional tastes, which were an outgrowth of the old family recipes. This uniqueness of production methodology is a large factor in the difference between modern miso and modern soy sauce, the currently established flavor of which is in fact a product of the simplification of varieties that accompanied its industrialization. This is a stark contrast to the many varieties of miso, the majority of which are largely the same as when they were being produced by individual families hundreds of years ago.
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An important factor in this is also the relative ease of production by hand of miso as compared to soy sauce. Soy sauce was, of course, also made by hand in the past, however the vast majority of it was simply a standard style. This style is now referred to as tamari and is separate from what is now considered standard "table soy sauce." However when compared to the process for handmade miso, tamari is much more time and labor intensive.

There is also one more reason why miso outlasted soy sauce as a handmade product, and that relates to its use at mealtimes. While soy sauce could be used with effectively any food and at any meal, miso remained set aside only for certain side dishes. Soy sauce, as well, is obviously a liquid, whereas miso is a solid. Furthermore, when producing soy sauce, the flavor is the only thing actually extracted from the soybean, while miso, in contrast, is able to preserve many of the nutrients intrinsic to soy.

Given all that, let us think for a moment. Imagine if you will that we have set before us some soy sauce, some miso, and some rice. If you wished to make the rice into a side dish for some larger meal, which would you use to season it, the miso or the soy sauce? Of course, if you were to use the soy sauce, the result would no doubt be perfectly edible, and most likely quite delicious. However in terms of nutritional value, the unanimous winner would have to be the miso. In the past, people made good use to miso's power in their daily lives, despite rarely ever being conscious of the fact that they were doing so. In the case of handmade daily meals, it only makes sense to use more miso. Furthermore, since miso is easier to make, people ultimately chose to buy soy sauce and make miso themselves. There you have it…the same origin, yet two very differents paths of development.

It may come as a bit of a shock, but did you know that miso actually has a deodorizing effect? Or rather, to put it more correctly, it is capable of absorbing various odors. For example, in the case of items such as miso fish, by inserting the miso, it will absorb nearly all the unpleasant odors of the raw fish. This effect is caused by the abundance of soy proteins contained within the miso. For this reason, miso tends to be used with foods that would otherwise have very pungent odors, and is especially common in dishes using fish. Another common example would be oyster hot pot, often cooked during the winter, which takes full advantage of these odor-neutralizing properties of miso.

There is, however, in fact a second half to miso's odor-controlling powers. If the first half was its ability to absorb unwanted smells, the second half is the smell of the miso itself. Naturally, there are some people who are not overly fond of the smell of miso, however with regard to the Japanese, these people are few and far between. It is most commonly described as a faint, savory aroma. However this smell is surprisingly powerful, easily capable of forcing out other smells. As a result, many people enjoy their meals with the pleasant aroma of miso in the air.

Having said that, though, leaving Japan and venturing overseas will lead to a different reception of miso than Japan's impression of appetite-inducing aroma. Miso is, afterall, a fermented product. As a result of this fermentation, it carries a very unique odor. However these days, miso is still being marketed around the world for its stronger personality versus soy sauce. While not bearing quite as strong a stigma as natto, though, in many countries miso's smell is still considered unpleasant, particularly in parts of the United States and Europe. In fact, there have been cases recorded of people such as homestay students being banned from making miso soup, even to the extent, in one rather extreme and absurd case, of being threatened with eviction from an apartment.

On the other hand, on the whole there seems to be no problem with the reception of miso across much of Asia, unsurprisingly. Fermented foods of this nature have for centuries been one of China's great cultural exports, therefore both miso and soy sauce have been widely assimilated into daily life across the majority of Asia, while still retaining the unique characteristics of each product. Then there is, of course, the type of miso soup that is native to Japan. Simply put, no matter where you go in Asia, the scent of fermented soybeans is an implicit part of average daily life.