How do you prefer passing on ID from view to controller when editing data?

[eluser]donald.tbd[/eluser]
So far i have used two ways to pass on ID from view to controller when editing a row.
1) On url row, for example form action = "news/edit/7", accessible in controller by $this->uri->segment(3).
2) Hidden field in form. For example <input type='hidden' name='id' value='7'>, accessible in controller by $this->input->post("id").

Witch one do you usually use? What are the pros/cons of each? Witch one is the the "right" or at least better way to do it.

Thank you!