Forum Moderators: open
Search Engines:
1) Don't like redirects
2) Would probably find it hard to find any reason to support redirecting domains to folders on another domain.
3) Would be somewhat likely to give you credit from a different site.
I would say host the second domain seperately. Also, when people refer to subdomains - they usually mean:
subdomain.example.com
Google does seem to treat these seperately. At least for some things.
However - using such a tactic to pump up your own PR isn't likely to bear much fruit.
Laurenz