Does any one is aware of information about the recommendations (performance wise and any size limitations on the xml data file) of which way to read xml data or write to xml data, and pros and cons of reading /writing one way or the other and recommended way to use classes in system.xml and system.xpath namespaces?

There are obviously number of ways we can achieve the desired results using those two name spaces. But it would be nice if there is any microsoft recommended way to use these classes (some thing like best way of doing stuff)

Pls share if any one has information.

thanks
nath