Difference between Apache rules to block libwww-perl

Server Config
1

Hello,
I want to know the difference between these rules and which is most effective to block libwww-perl with the file .htaccess

SetEnvIfNoCase User-Agent "libwww-perl" bad_bot
Order Deny,Allow
Deny from env=bad_bot

or

RewriteCond %{HTTP_USER_AGENT} libwww-perl.* 
RewriteRule .* – [F,L]
2