Stills vs Motion
When a still photographer photographs people they are able to quickly capture decisive moments. For the most part they are reacting to what is happening in front of the camera. Those who do it the best are good at anticipating a moment, but still the are reacting to how people are behaving in front of them. Most photographers are able to shoot from their heart because when something moves them they are able to capture it.
When a videographer captures something over time. They start rolling and then stop at some point. They cannot just react to a moment and turn the camera on. The videographer must think about what they want to capture and plan out their coverage.
The major difference with shooting stills [photographs] and motion [video] is shooting from their heads. They cannot shoot from their heart. They must plan their shot more than the still photographer.
Using Your Camcorder by Mandy Matson.
Every book on capturing motion will address the need to plan your shots list out before hand. You will find every one recommends storyboarding your shots so you have a good idea of what you are planning to get.
As far as just capturing daily life it is rare to get the same emotional content that a still photographer will capture because they cannot just react, they must plan their shots.
When filming for a movie they not only shoot to a storyboard they must create the emotion through the actors. As we know there is usually one angle that can improve the emotional moment than another. Many times the storyboard will have multiple camera angles to jump from to help make this work. They are filming Dumb and Dumber here in Atlanta. Take a look at some of the photos shot of the set by John Spink the AJC photographer here. You can see the same scene shot by John from what is two different places on the set. The reason he was able to do that, is they will redo the scene over and over for different camera angles or variations from the actors themselves.
When in the editing suite they are picking from multiple camera angles and different performances to then craft the scene.
As you can see to shoot video the head is how it is done and not reacting from the heart in the moment.
The one thing that video does have over stills for capture emotion is the sound. This is why a good amount of the evening news footage that is moving is often the interview where the human voice is what is conveying most of the emotion.
Television news knows the power of the still and use it all the time for major news events. Eddie Adams photograph from the Vietnam War of the officer shooting the prisoner is seen all the time on the news when they talk about the war. They had a film crew who caught the entire shooting, but it is the still image that capture the emotion even stronger or they would not be using it over the film.
I believe many of our iconic photographic images of people are where a photographer caught a microexpression. A microexpression is a brief, involuntary facial expression shown on the face of humans according to emotions experienced. They are very brief in duration, lasting only 1/25 to 1/15 of a second.
Most people do not seem to perceive microexpressions in themselves or others because they cannot freeze the moment to see it. You must slow a video down and look frame by frame to see them and running at full speed the average audience will not see them. This is why I think video has a more difficult time to capture emotions.
The Wizards Project was a research project at the University of California, San Francisco led by Paul Ekman and Maureen O'Sullivan that studied the ability of people to detect lies.
Truth Wizards use microexpressions, among many other cues, to determine if someone is being truthful. The Wizards Project has identified just over 50 people with this ability after testing nearly 20,000 people. So the research pretty much shows that in real time most people miss microexpressions.
For me the power of the photograph is if they capture the "Decisive Moment" then the truth telling makes this a powerful storytelling medium. The photograph can capture the storytelling moment that communicates emotion, because the audience will have time to see it and absorb the moment.
Video or Photograph?
I believe from all my experience that the best visual storytellers are using both their head and hearts.
The still photographer uses their head to plan to be in the right place at the right time. They are able to anticipate moments due to their knowledge of human behavior on a particular subject.
The videographer know how to craft a sequence that will pull on your heart as a package. From their experience they know what has moved their heart in the past.
My suggestion for those telling stories of life happening and not creating stories with actors, is to do like so many news outlets do when it comes to communication news events with a lot of emotion--use stills and the human voice to pull the audience in.