Merge two folders with a lot of sub folders and files

I have a situation where there are two folders that need to be merged to one.  The folders are about 8gig in size and contain many levels of sub folders with documents and some images.  The documents are going to be mostly xls, xlsx, doc, docx, ppt, txt, pdf, jpg.

Many of the files are duplicates although one folder may have a more recent document.

Folder A
-- SubFolder A.1
---- SubFolder A.1.1
------ Document A.1.1  somefile.docx last mod 6/12/2015 3:45pm
-- SubFolder A.2
---- SubFolder A.2.1
------ Document A.2.1  somefile.docx last mod 2/21/2015 10:21am


Folder B
-- SubFolder B.1
---- SubFolder B.1.1
------ Document A.1.1  somefile.docx last mod 1/1/2015 1:20pm-- SubFolder A.2
-- SubFolder B.2
---- SubFolder B.2.1
------ Document B.2.1  somefile.docx last mod 6/5/2015 12:53pm

This is on Windows Server 2008


My goal is to Merge everything in Folder B to Folder A where only folders and files get added to A from B that are not in A and only files from B get copied to A if they are newer than in A

Am I better off writing a vbscript or using something like RichCopy?