I have place in my group for one of these two, since I ditched Jaheira.
Anomen is a sissy fake paladin who doesn't know how to wield a sword, and with an annoying attitude, and Keldorn is a true paladin.

My question is, which of these two is more interesting for the story-line, character-interaction and subquests? (Please do not reply with answers about whom of the two is better, who can wield that Holy Sword of Dragon Slaying in One Strike +8 etc).

I have heard a rumour that it's possible to make Anomen what he strives to be, a true Knight, through some quest, and that seems interesting. About Keldorn I haven't heard much yet.

ps, I haven't met Cernd yet, but if he is also an interesting character story-wise etc, I might also consider having him join my party.

Personally I would take Anomen, because
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spoilers below!
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Keldorn will leave your party after a short time, and you won't be able to get him back. You invest XP and items into him and poof! Bye-bye.

Anomen, OTOH, can become a member of the order if you handle things right which will get him a stat increase. Also, he becomes much happier (less pissy) once he becomes Sir Anomen. Finally, if you put the girdle of Hill Giant Strength (str 19) on him and give him a good mace like Ardutia's fall, you won't miss the sword, I guarantee it.

As for Cernd, his stats are pathetic until he shapechanges, but while in his other form he can't spellcast. I like his voice and his picture, but nothing else about him. YMMV, of course.

I have had Keldorn since the start of the game, and am in the Underdark and have done several side quests so I would disagree that he leaves soon after he joins. I haven't had a quest for him except to help the church, so I don't know that he's that interesting. However the dialog between him and other party members is interesting.

Not sure about Amoween since he seemed like too much of a weenie to me

i am using keldorn now. he work out very good with the +5 sword and his magic resistance. he did mention to do one last quest before return to his wife. my question is will he leave after i srescue imoen? i am at that chapter now? thanks

I had Keldorn in my party and he left for 3 hours then returned. I had him through to the end conflict (which all my party survived... thanks to the rod of resurrection )
Cheers