How should be my Service method signature?

I'm using a Service Layer, and until now I used a ServiceObject (which implements ArrayAccess, Iterator, Countable) but I'm wondering if it's a good ideas.

Would you do:

ArticleService::createArticle($articleData, $userId);

or

ArticleService::createArticle(ServiceObject $data);

where $data are:

array(
  'title' => 'Lorem ipsum',
  'body'  => 'Dolor sid amet',
  'userId' => 55,
);

The ServiceObject has the benefit to provide a common Signature for every method, however sometimes it doesn't look efficient, and it is not widely used, it loses its interests.

Any feedback?