Which Schema to use?

I am starting to develop a schema for our application.  Am at a loss as to
which schema spec to use.  The W3C standard is obviously not yet out (when
will it be finalized?).  Should I use Microsoft's (we develop in VB and C,
hence I will be using their DOM implementation anyways) Schema, or what is
provided at their Biztalk.org site (what is the difference between the two
anyways, and if they are different, why did MS have to come up with two
different schema sets?) or should I use a third party product like the few
listed in this list, or should I go with DTD?  Is there a robust schema spec
that fully implements the current W3C standard as proposed and has a fully
functional parser/validator?  Tx for any suggestions.
 
Enis Bengul