No reason specifically, when I searched the forums here and looked online most people recommended doing a 301 redirect because it tells search engines that the page has permanently moved to the following location. I have just applied this redirect to one of my sites a couple days ago so I can let you know how well it goes. So far it has worked perfectly and my rankings haven't dropped, but I have to see if they get replaced with the new domain.
This is the scenerio... I have two sites currently, Site A and Site B both pointing to a same site. Technically, there's a reason for that. Since a word from Site is blocked, we made Site B the alternative but the real brand is the Site A. We did some sort of an aliasing. Now, I want to ask from an SEO stand if Aliasing or 301 redirect will be best for this problem. Any suggestion will be highly appreciated.
If you're doing it to bypass a word filter, then a 301 would break that. The plus side to the 301 would be not worrying about a duplicate content issue between the two domains. You could probably show different robots.txt files depending which domain is requested, having your normal one on the main site, then on the other one block the search engines with something like: User-agent: * Disallow: / I didn't test this, but you could add something like this in the .htaccess file... and we'll assume the above lines are in robots2.txt. RewriteCond %{REQUEST_URI} /robots.txt RewriteCond %{HTTP_HOST} the-mirror-domain.com RewriteRule .* /robots2.txt [R=301,L] Just replace the-mirror-domain.com with whichever domain does the mirroring to bypass the word filter. That should keep the other domain from getting indexed and let the search engines focus on the main site. It's also not a sneaky cloaking issue to worry about, since it applies to all requests, so Google etc... sees what anyone else would see.