Google Scholar (GS) does not show what websites or databases it covers. As a consequence, we cannot be sure that the search is deep. Neither can we be sure that all the results are from reliable sources.
There is no way the user can sort GS's results according to the number of citations. GS sorts its results by relevance only, as GS's algorithms interpret it (I don't know how they do it). As a result, the user might miss a highly cited material which GS's algorithms sort as not relevant enough. However, from my experience, this is unlikely. There is a software called www.harzing.com which can download GS's results and sort them by the number of citations.
GS shows articles and books from google books and it does not allow the user to see articles only.
GS does not allow the user to sort results in relation to the publication's field and authors' affiliations as academic.microsoft.com does.
GS's "My citations" section does not allow the user to sort citations by year.
Also, the user cannot see updates from scholars s/he subscribed to in the form of a "wall" or "feed", as one might on facebook, researchgate, or academia.edu.
Read more about academic search in this book: Mann, Thomas. 2015. The Oxford Guide to Library Research. 4 edition. Oxford ; New York: Oxford University Press.