While there is no objective way to know the answer to this question, I would argue that music has had the greater impact. This is because it is more pervasive than TV and it tends to be ahead of the rest of society more than TV is.
To be sure, TV has had a tremendous impact on our society. It has helped to shape our fashions. It has helped to create celebrities. People have become entranced by “reality” shows such as “American Idol” and “The Bachelor.” Even so, I would argue that music has been more important.
One reason for this is that we tend to be in contact with music more often than we are with TV. We can listen to music in our cars, as we exercise, and in many other situations. TV, particularly in the days before iPads and such things, was something that could only be consumed in our homes.
A second, and perhaps more important, reason for this is that TV has tended to lag behind the times. It is older adults who decide what gets put on TV and they are generally the ones who watch more TV. Therefore, TV shows do not tend to reflect the ways in which society is changing. In 1966, with the Vietnam War raging and the counterculture and sexual revolution going, the top shows on TV included Bonanza, The Andy Griffith Show, its spinoff, Gomer Pyle, U.S.M.C, The Lucy Show, The Beverly Hillbilles, and Hogan’s Heroes. These were not shows that captured the zeitgeist of the ‘60s.
For these reasons, I would argue that music has had more of an impact on society, particularly when it comes to driving social change.