Forum Moderators: open
A redirect is just an instruction telling web and/or DNS servers, "When someone asks for www.A.com, send them to www.B.com"
[edit] If you have two domain names pointing to exactly the same site, I would only use the .com address for site promotion... but someone else may disagree on that point.[/edit]
However, I once promoted a site that only needed a short window of operation -- about two months. In such a case, I didn't worry about duplicate pages getting dropped, I just registered all the URLs.
But then there is the problem of a regional search engine not accepting a .com
If the site is regional, then the regional domain is the more important one to promote.
It's safer to have only one site (regional) with the .com domain simply pointing to it - ie a redirect.
I would say a regional URL is unnecessary if you have a .com address already. If your regional information is in a separate area of the site, just submit the front page of the regional content area to regional directories under the .com name (http://mysite.com/regional_area/index.html).
Alternatively (but still unnecessary IMO), you could set up the .com URL to lead to the site's main page, and set the regional URL to point to the regional content area front page.