Question about wp_dropdown_users()..

If I want to create a plugin that took the default arguments for this function (found in users.php) wp_dropdown_users() and sets them to something different, how would I go about doing that? Would it be a filter or an add action?

Specifically I need to change:

'show' => 'display_name',

to

'show' => 'user_login',

in the $defaults array. I’m sure this is really simple, I just can’t get the arguments to pass through my function in the plugin correctly.

Thank you!