Why did man decide to domesticate cattle belonging to Bos rather than
Bison? Was it a question of geography, characteristic, or both?
My first speculation was that size matters in this case, which is an idea that I will explore first, but upon further consideration, I think that this is partially right for a different reason and that the amenability of Bos to providing farm labor relative to Bison may have been the most important factor.
At the time that cattle were first domesticated (something that probably happened a number of centuries after the domestication of sheep and goats, and tens of thousands of years after the domestication of dogs, but several thousand of years before the horse was domesticated (and before the hybrid mule was available), and a dozen centuries or so before donkey were domesticated) human communities were much smaller than they are today. A community with 200 people in it would have been a major city. A few dozen people in a community would have been pretty typical.
Bison are much larger than Bos, on average. This means that the same amount of pasture can support fewer Bison than Bos, and that each Bison slaughtered will produce more meat at once. Slaughtering more meat than your community members can promptly eat in a week or two is going to produce lots a wasted meat that your community spent a lot of time and effort nurturing. But, if each slaughtered animal is smaller, it is easier to eat a larger share of the meet from the slaughtered animal before it spoils and is wasted.
Indeed, even modern cows are probably bigger than the earliest domesticated Bos. So, meat production from slaughtered cows could be broken up into more manageable installments.
Upon further consideration, I still think that smaller size was an advantage for Bos, but I think that it may have had less to do with the amount of meat produced per animal slaughtered (after all smoking and/or salting beef to preserve it must have been mastered quite early on, probably even before herding and domesticated animals were developed), and it had more to do with a few other factors related to size:
Smaller animals eat less, so cows are more useful than Bison if you have a limited supply of grazing land available (and early on in farming the Fertile Crescent where cattle were domesticated had a lot of forests that were cleared by early farmers for crops and much less open steppe pasture than it does now).
Smaller animals are easier to control while using them to carry out farm labor than bigger animals like Bison, particularly for early herders whose animal control skills and techniques may not have been very sophisticated.
To the extent that you want to prevent your cattle from walking off away from your farm with fences or rope leads, for example, it is much easier to restrain a cow than a Bison. You need bigger fences and stronger rope to restrain a Bison.
At least in the winter, it appears that early Neolithic farmers may have used the common area of their homes as a combined family room/cattle barn. While having a bull in the China shop is bad, having a Bison in the China shop is worse. The comparatively smaller cow would have been preferable to the Bison to share your family room with on a bitterly cold night (in part to provide the humans with additional indoor heat from the animals as well as for the benefit of the animals who are protected from cold and wolves when indoors). Of course, sheep and goats would be better still to have indoors, but neither sheep nor goats are well suited to serving as beasts of burden, so there wouldn't have been any substitute beasts of burden to the cow at least until the donkey was domesticated in Egypt, after the European Neolithic Revolution had already started to expand into this "virgin territory" from a farmer's perspective.
A related consideration is that before a cow, particularly a male cow, becomes food, it is also a major source of muscle power for all manner of purposes from hauling sledges (carts would only come thousands of years later), to clearing forests, to ploughing fields. I've seen other members of the Bos genus of several species used in this capacity, but I've seen a lot of American Bison (the city where I live owns its own Bison herd), yet I've never seen one used as a beast of burden and I seriously doubt that Bison would be well suited to this role.
Bos also has a longer lifespan than Bison (36 v. 25 years in captivity and proportionately less in the wild). If meat is the primary objective, this makes Bison is superior, but if you want a beast of burden, you would prefer a longer lived animal. This fact is suggestive of the idea that cattle may have been domesticated primarily as a source of power for horticultural efforts and only secondarily as a food source in its own right.
A beast of burden first, food source second model is also consistent with the reality that eating the grains that cattle eat directly is about tens times as efficient a source of calories as eating beef. You don't want to waste precious grain growing capacity on cattle feed and thereby reduce the percentage of grain grown available to feed people on cows, unless the cows can do work that increases total grain production by more than their own dietary needs reduce food production. Getting enough calories was the primary consideration in the early Neolithic period - population densities were increasing by a factor of as much as 100 fold as quickly as population growth could get it there, while calories per person actually fell from the previous hunter-gatherer era to the early Neolithic before humans had fully mastered farming. So there would be considerable pressure to use domesticated beasts of burden the wasted less calories than Bison would.
Another piece of corroboration for the beast of burden first, food source second model for cow domestication is the popularity of the mule on small family subsistence farms in the U.S. as late as the mid-19th century (recall the swan song of "40 acres and a mule"). It is much harder to cultivate enough crops to feed an entire family without a beast of burden than it is to do so with one.
But, mules are even smaller than cows which makes them desirable on a small farm because they eat less, yet are still big enough to get the beast of burden jobs done and are more manageable than cows. Did you know that cows kill more humans every year in the U.S. than poisonous spiders, gila monsters, snakes and sharks combined? Mules, not so much.
The benefits of mules relative to cows as beasts of burden on small farms like those of the early Neolithic era due to their smaller size would apply equally to smaller than modern cows relative to European Bison which were apparently bigger and wilder than American Bison.