I very much doubt that you are going to get an objective answer to that particular question, until you come across anyone that has implemented the same database (schema, data, etc.) on both platforms.
However given the fact that you can find millions of happy users of both databases, I dare say it's not too much of a stretch to say either will scale just fine (I've seen a snappy Sql 2005 implementation of 300 TB that seemed pretty responsive)
