which is faster: XML or mySQL?

[sprocket]

I am aware of the benefits of both XML and mySQL databases, and currently use mySQL extensively for all data storage.

However, I'm getting around to providing one of my tables (the 'products' table) in XML format, so my users can access it for their own needs. What I want to know, is it going to be faster for my webserver to access that flat XML doc than it is to query the database for retrieving info on the products?

My scenario -
The products database currently has 1500 entries, with a heavily used index on the categories (category) field. Whenever the webserver calls the table, it is usually only with a "SELECT * FROM products WHERE category REGEXP '30.3' " or something like that.

THe product can belong to numerous categories, hence the need for some form of REGEXP match.

Would I benefit (in speed and processor usage) if that entire table of 1500 products was flattened into an XML file, and have PHP scan the file for whether to display the product depending if a <CATEGORY></CATEGORY> entry matched the required category?

Of note is that the products database is continually being updated with new products, and price changes, so I would still keep the mySQL products database handy and generate a new XML file everytime the database was updated.

Thanks for any insight...