smarty vs. patTemplate vs. includes - newbie q

Hi, I'm designing a site with about 100 different pages. I'm debating whether to use a template mechanism such as smarty or patTemplate vs just creating pages and including the body templates based on the url parameters. I realize you get a layer of abstraction using the template mechanisms, but with the scheme that I have in mind the users will only be editing the pages that are marked body_foo.php. These body pages would be basically pure html, so they can't really screw anything up in the php logic. They would be called off an index.php that has a bunch of includes, header.php, body.php, footer.php etc, this page would be off limits to the user for editing. From what I understand, both smarty and patTemplate are popular and both have supporters and detractors, is one template significantly faster or more stable than the other? If I just use includes, am I gonna run into problems, other than the loss of elegance and some abstraction that a template system might offer. My site will have approx 100 pages, with a peak of 600,000 hits per day. thanks for your help, Dave