For majority of queries, mysqli is only a fraction faster, and converting our whole script to mysqli would take a lot of work. I decided that at this time it was not worth it, as PDO is also very versatile and lightweight. For other users starting their script, I would recommend using mysqli if you are very familiar with mysql and would need any speed increases possible, everyone else should use PDO.
Another note: md5 is case-sensitive! If using indexes as I have stated above and using tables with md5 first letter, then remember to do strtolower() for indexes and before doing md5! I will keep this updated with any new things I come along.
