When comparing the terms "Searching" and "Looking" you have to consider the way in which the reader envisions the term. "Looking" is a much more common and informal term in the situation you described. This is because you can "look at" things without much effort involved. When you say you are "Searching for (insert direct object)" it implies a more intentional and involved approach. Therefore, if you are writing a letter or filling out a resume, you will want to use the term "Searching" to sound more professional. If you are just chatting with your friends, either is fine.