I have a basic question about developing mobile sites for clients.

From what I understand, you can create a single site that's optimized for both desktop and mobile devices, using either a responsive design or some CSS tricks.

Or you can use a service like www.mobisitegalore.com or a WordPress plugin to convert the site on-the-fly for mobile devices.

Or you can create an entirely different mobile site.

Assuming I've got that right (please correct me, if not), what are the pros and cons of each and which do you prefer?