I think you're incorrect in saying that no one is experienced in .NET.  
It is considerably newer than Java, but still has been around for a
number of years, and the languages are at least similar to pre-.NET
languages in important ways.

Your desire to do low-level C and C++ code is not related to this
situation.  If you're looking to write low-level native code, you'll
have to do it with a language that's different from Java or any .NET
language.  (Note: No, C++ is not an exception.  Contrary to popular
belief, you cannot write .NET code with C++.  You instead need to use a
different language called "C++/CLI" which is basically Microsoft-
proprietary and rubber-stamped by the ECMA.)

As for whether to use Java or .NET, it depends.  .NET code is basically
Windows-limited and integrates better into Windows environments,
especially if you're working with COM and the like.  Java is more
portable, generally easier to get into without breaking the bank (for
individuals; for large corporate environments, tool costs are largely
irrelevant), and is more mature and has a larger amount of third-party
corporate and open-source supporting structures and code base.

   If you take a programming newbie, and a programming veteran who happens
to have zero .NET experience, and you assign both of them to a .NET project,
the veteran is probably going to whoop the newbie's butt. While both parties
might not know the .NET API very well, the veteran will have experience with
object oriented programming, design patterns, asymptotic performance
analysis of data structure and algorithms, etc. giving that person a huge
edge of the newbie.

   - Oliver

If you are looking for hard numbers, do a search on dice.com and
checkout the # of job opportunities for each technology.  Would give
you an idea which has the greater following, at least per job
availability.