Google Scholar is an open-access way of distributing information about scholarship.
However, the absence of quality control in this tool can be an issue. Sometimes a publication will show up in Google Scholar multiple times, due to subtle differences. This seems to occur with highly cited publications. This can artificially amplify the citation count seen in Google Scholar versus what you will see through Research Experts. The Scopus-based citation count refines publications to ensure they only appear once.
The Scopus-generated H-index is more reliable and will generally be lower for every investigator than the Google Scholar H-index.