If you are the administrator of your server, I would not use any of them and prohibit IP addresses at the firewall level - thus, Apache or Apache + PHP will not have to work.
If you are not an admin; well, it .htaccessmeans only Apache, and PHP does not load / compile / execute; I assume that only Apache (i.e. .htaccess) should require less resources than Apache + PHP.
: / IP- , ?
( PHP-...)