It's interesting that even though we see the world in color, when choosing the final “look” our photos will have, black and white is still so high on the list of choices. It makes perfect sense, though, given its prominence in the evolution of photography.
There are certainly advantages of using color, since after all, this is how we experience life. Using color is very effective when it’s paramount in telling the story. The use of color can communicate the time of day, period in history, or even something as simple as what the weather may have been like. Cool tones may suggest the feeling of a brisk morning or night, while warmer tones may suggest a hot summer day. These tools can also be used to suggest the emotional tone. Since the dynamic range of color is vase, especially in digital photography, you can take the same image, give it two completely different final edits, and effect its viewers in two completely different ways. Just think about how much time people spend putting filters on their images before they post them on social media. It’s because colors produce involuntary emotional responses in people. This is why color correction in film post-production is so very important. The filmmakers know that this is vital in suggesting the emotional tone of the film. Imagine if The Dark Knight used the same scheme of colors that Charlie and the Chocolate Factory used. And Vice Versa. I’d dare say they tried with Batman and Robin, but we see how that turned out. ;-)
As with many things artistic, I could also say that Less is More. In many cases, the less color utilized the more impact you can make. Sometimes too many colors can be distracting and leave you unsure what the focus should be. B&W photos, or monochrome, have a way of getting right to the essence of what the image is aiming to convey. We all have different emotional associations to color. If as an artist, there is something specific you want your photo to project, try simplifying it by removing color from the photo. Putting the image in B&W forces us to concentrate on the emotional tone the photo is aiming to convey, because it’s not suggested for us by the use of color. The photographer may heavily utilize dramatic contrast between the light areas and shadows. The reason many still prefer B&W portraiture is because it helps the viewer focus on the emotion state of the subject, which is easier to communicate when there is just one scale; black, white, and the gray tones between. The below photos are an example of that.
There is also a certain ‘timeless’ element a B&W photo can have that the color may not.
Below is another example. However, in these images, I’d say the general tone is better conveyed in the color portrait.
Then inevitably, there are times when using Color or B&W is equally effective. It just becomes a personal preference. Something to also keep in mind is that certain colors that are very distinguishable when shot in color may not be in black and white. Red and green would be an example of this. These color tones are easy to decipher in a color image, but when shooting a monochrome image it would be more difficult to differentiate them. In a monochrome image, the way that light responds to someone wearing a red and blue shirt is a lot closer than the way light responds to a brown and yellow shirt.
Whatever your choice be, remember they are preferences. What affects one viewer one way, may germinate a different feeling from another. So go out and shoot. And if your camera allows, remember to shoot in RAW format. Although the files are much larger, it will capture the most information, and this will allow for the most preservable file conversion to color or b&w in post.