Hey,

Data science is basically extraction of various form of data from available structured or unstructured data. You need to apply this date over various application domains. It will need algorithms, process and scientific methods. Web development, on a general note, is designing of website. Both these fields are good in terms of prospects, career opportunities. You need to figure out your interest and in which field you have more passion or your knowledge lies greatly in which field, and make a choice accordingly.

You can know about both these fields over here:

Web development: https://www.careers360.com/careers/web-developer

Data Science: https://www.careers360.com/careers/data-scientist