Here's a breakdown:
* pagbigkas ng talumpati - literally translates to "delivery of a speech"
* nang walang paghahanda - means "without preparation"
* pag-uusap - refers to "conversation"
* nang walang pag-iisip nang mabuti - means "without careful thought"
Therefore, you can use either phrase to refer to extemporaneous speech in Tagalog.
However, depending on the context, you might also use other terms like:
* pagsasalita ng impromptu (impromptu speaking)
* pagsasalita ng patulad (speaking like a poet)
* pagsasalita ng ad-lib (ad-libbing)
Ultimately, the best term to use will depend on the specific situation and the level of formality desired.