codeigniter session

[eluser]global_erp_solution[/eluser]
I'm creating a form to autenticate users. Now, in many tutorials there are two different approach. Some are using $this->session

Code:

$this->session->userdata('user');

while others use:

Code:

$CI =& get_instance();
$CI->session->userdata('user');

what's the difference between these two? any different effect or consequence for using each one? thanks.