When is xml better than just external text?

So, I’ve seen external xml used for flash data display, but was wondering about its usefulness for blog, narrative, site copy etc.

Or, does everyone stick with external text file (instead) for that use?

(I was hoping to get the searchability of the external xml copy, but if it isnt used well for site copy, the text method will be more favorable I guess)

Any input??

Thx