last months while programing ABM 1.1.0 I've tried Akismet, Stop Forum Spam, BotScout and Project Honey Pot single and separatley for serveral days and weeks on my support & test forum. My statement is based on these comapring tests and experience.
The authentication is important for reporting new spam only. And here all HTTP blacklists are requiring a key. But BotScout and Project Honey Pot only have an user frontend on their websites to report new spam manually.
Which version of Advanced Block MOD do you mean? When have you tried it?
In ABM 1.0.10 a new feature/setting has been added not to check posts of registered users. phpBB3 by default is checking all posts with check_dnsbl.
But please note that Advanced Block MOD 1.1.0 is a completely new generation of the MOD.
Advanced Block MOD support you can find under http://www.phpbb.com/customise/db/mod/a ... block_mod/
. IMO this is the best place for feedback about ABM, too.