I hate defining each variable if I don't have to.
Using extract() in this case could lead to the problem for which register_globals was disabled by default in PHP 5. Read the PHP manual on (Not) Using Register Globals and warning in the PHP manual entry on extract().
The skinnier the code, the better.
That's true as long as readability, security and required efficiency is not sacrified. (Oh, and of course, if the code works as specified. 🙂 )