How much you know about your area of research and your respondents will determine exactly which kind of research is right for you. Both types are important and most people will need a combination of the two to get the most accurate data.
Qualitative research is by definition exploratory, and it is used when we don’t know what to expect. This helps to define the problem or develop an approach to the problem. It’s also used to go deeper into issues of interest and explore nuances related to the problem at hand. Quantitative research, on the other hand, is conclusive in its purpose as it tries to quantify a problem and understand how prevalent it is by looking for projectable results to a larger population.
We should use both qualitative and quantitative research since they provide different perspectives and their goals usually complement each other.