Using robots.txt to create thematic flow on large site

Or, better to create smaller thematic subsite.

[latimer]

We are debating the benefits and drawbacks of two approaches to building thematic focus.

1. On large site with huge offering of pages and wide variety of topics we would use robots.txt to restrict spiders from folders in the site to create thematic flow. Visitors still have access to the other areas of site but the spider only get the pages realted to the theme.

2. Create smaller site with the content of the theme. Allow spiders access to entire site.

Any thoughts on these two different approaches?