Nothing or "" when using VB Script in a workflow

What is the proper syntax to test for an empty result when using VB Script in a workflow after looking up a value in a File Cabinet or external data source?

For example, Using a file cabinet lookup that should return VendorName, then updating an index value of the document with Iif().

So should I use

Iif(GV_VendorName = Nothing, "No Match Found", GV_VendorName)

or

Iif(GV_VendorName = "", "No Match Found", GV_VendorName)

or are these statements equivalent?

Any and all clues appreciated,

Based on advice from DocuWare techs a couple of years ago I use both of those, GV_VendorName = Nothing OR GV_VendorName = "", that way my bases are covered