Uno dei motivi per usare VB.NET per parlare con 
Office:
  It's not that it's difficult to convert code from Visual Basic .NET to 
  C#, or to simply create code that automates Word or Excel in C#. What caused 
  me pain in this particular project was that when you attempt to communicate 
  with objects designed to be consumed by VBA clients, you're living in a world 
  that didn't take C# and its design goals into account when it was being 
  created. One thing is for sure: because of its VBA lineage, it's a lot easier 
  accomplishing Office automation from Visual Basic .NET than it is from C#. I 
  can't dig into the details here, so I'll just point out a few delectable 
  tidbits, with links to more info later on.
Fonte: { End Bracket }: C# and VBA: Like Oil and Water -- MSDN Magazine, February 2005