I'm working in the Codeigniter framework, and want to send requests to my controller/model that have several variables involved. Is there a difference between passing those variables via a hidden form (i.e. using "post") as opposed to passing them through URIs (e.g. 'travel/$month/$day/')? What about security concerns?

e.g.

URIs:
http://www.example.com/travel/$month/$day/

Hidden Form:
form_hidden('month',$month);
form_hidden('day',$day);