I'm new to posting on Dakka. I did the reading only thingy for quite some time and just felt the need to spare my thoughts. (If you want to read them? I don't know anyway...)
I would say warseer and dakka are probably the both biggest forums without a dedication towards one or another
40k faction. (As this is the only wargame I play
atm.) None of the two is better overall. They are quite different...people here are not either whining about clown taxis 24/7 or whining about people whining about them fielding the tri-falcon-unbalancedness. Maybe I'm reading the wrong threads...but that's what I've seen.
And you can pick up some good advices for overall competetive play, tyranids and probably a few other armies. Yes, some posts are pretty harsh and sarcastic, maybe even ignorant, but personally I can cope with it.
On the other hand, there is no place like warseer if you seek advice for Witch Hunters or questions on rules. People are either very polite and diplomatic or, in contrast, dickheads who insult you right away.
The two sites are more a symbiosis for me, not opponents, who must be better at all cost and in every facette.
Bolter&Chainsword doesn't work out for me. I don't like their army list writing philosophy and I'm more a player/theoryhammerguy than a painter or artist. They got a nicer color theme...