No. The default namespace never affects XPath expressions. //order
always selects order in no-namespace in Xpath1 and selects order in the
xpath default namespace (which is not set by xmlns="...") in Xpath2.

It is adviced not to use default namespaces in XSL stylesheets, though.

You should use them, but for controlling literal result elements in the
result, not controlling xpath queries into the source.

Cheers,
Geert