I would recommend the MCITP on the basis that it is more current and has less exams.

If you can use 2005 you should be able to use 2000 due to the fact that it's functionality is largely a subset of 2005.

If you work with 2005 regularly you should not have too many problems passing the exams.

I passed them and have never used 2005 for any real work as we only use 2000 at present.