I came across an article titled "Efficient 301 Redirects."
For example, if you are trying to redirect your site from www to non-www domain, the article suggests that when compared to this .htaccess/httpd.conf rule:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.domainname\.com$ [NC]
RewriteRule ^(.*)$ http://domainname.com/$1 [R=301,L]
</IfModule>
this would be a more efficient 301 redirect (although only slightly):
<IfModule mod_alias.c>
Redirect permanent / http://domainname.com/
</IfModule>
Question: Is the latter rule really efficient (even slightly)?