There are different ways to search in PubMed, each with their own benefits.
Example Using MeSH
Example Using Advanced Keyword Search
Example Search
One advantage to using Web of Science is the ability to do citation mapping. Click on "Times Cited" (see below) to see article citations that cite the article at hand. The articles will necessarily be more recent and may give you more material on your topic.
One advantage to using Google Scholar is the ability to do citation mapping. Click on "Cited by" (see below) to see article citations that cite the article at hand. The articles will necessarily be more recent and may give you more material on your topic.