Mcafee- AVG

A friend of mine downloaded mcafee viruscan, but got rid of it and downloaded AVG because the mcafee was taking over 4 hours to scan his computer.  He said he remembers that when mcafee was done scanning it said it had gone through like 30,000 files, and now when he scans with AVG, it goes through roughly 15,000.  Does this mean AVG isnt scanning some things it should be or that it is less thourough than mcaffee?