MSA

Masters in accounting  which are called different names, such asMSA, Master of Science in Accounting, Master of Accountancy but are all essentially the same thing. So when you hear these different types of Masters in Accounting they are referring to a very same degree. However MST ( Master of Science in Taxation) is a different degree. As the name implies it is focused more on tax side of accounting.

Why do people go for MSA?

The biggest reason many people go to get their MSA's is simply because they want to fulfill the 150 credit hours requirement. If you didn't know, then most, if not all of public accounting companies require you to have 150 credit hours before you start your employment simply because it is a requirement to sit for a CPA exam.
Since most of students who get their undergrad degree usually only have 120 credit hours, they go ahead for their MSA since it usually last only around a year and it gives 30-36 credit hours.

Do you need to go to a top school?
Many of the professor I talk to say that it doesn't really matter where you get your MSA from, as long as Big Four companies come and visit your school. However, my personal opinion is that it does matter although not as much as when your are getting your MBA. So do your research and don't just take my word for it. Ask around people who have went to good schools, professors, recruiters or even just friends. So do you homework.

Top 10 MSA programs.
Based on USnews.com rankings.
 1   University of Texas--Austin (McCombs)
      Austin, TX
2 University of Pennsylvania (Wharton)
Philadelphia, PA
3 University of Illinois--Urbana-Champaign
Champaign, IL
4 University of Chicago (Booth)
Chicago, IL
5 University of Michigan--Ann Arbor (Ross)
Ann Arbor, MI
6 University of Southern California (Marshall)
Los Angeles, CA
7 Stanford University
Stanford, CA
8 Brigham Young University (Marriott)
Provo, UT
9 New York University (Stern)
New York, NY
10 Indiana University--Bloomington (Kelley)
Bloomington, IN