Best in what regards? DALnet is the best when it comes to oper/user communication and services. Undernet is best when it comes to security. Efnet just plain sucks. No services, oper vhosts, too much vanity kills, and way too many kills for personal reasons. Then again, that's why other networks exist, because of Efnet's corruption.
I could also go on to say why my network rules
, but your topic covers only the 3.
