Official XHTML 1.1 DTDs vs. official XHTML 1.1 XML Schemas

Question

I have the option of validating XHTML 1.1 documents against the official XHTML 1.1 DTDs (I use the plural because the "main" DTD actually includes several others) or against the official XHTML 1.1 XML Schemas.

Now I know that the XML Schema language is more expressive and powerful and can therefore check for more things. What I'm wondering is whether these "extra" features are actually in use in the official schemas. To put it differently, will validating against these schemas check for more things than validating against these DTDs?

Answer 1

There are many things that you can only express with a schema and than means that validating against a schema will always give you a better response about the validity of your XML file.

Answer 2

It's a requirement that anything that validates using the DTD should also validate using the schema.

The conformance definition states that

The document MUST conform to the constraints expressed in Appendix C.

and Appendix C contains the DTDs. Nothing is said about conforming to the schemas which are in Appendix D. Therefore, any extra constraints from the schemas would not be binding, since documents only need to satisfy the DTDs.

(Edited)