Please tell me which tank is better ourdays for tanking raids and especially mythic + content BDK or Guardian Druid?
I dont like other classes only Guardian and BDK.
When i say better i mean
Blood DK. 
^ he’s biased.
Go bear.
I have done 10 mythic bosses as dk (just for fun instead my usual monk before the nzoth bodyparts), but as druid only HC, so I cannot fairly comment, but both work well in nyalotha, but dk’s cds are so good that they can go full offensive, and ams/tap do the rest, and was most enjoyable tanking I had done. In Nyalotha I would take bdk for ‘fun factor’, but both do ok. Duids favor is that they can put so much corruption that their nosebleeds and they outheal it with ease.
It really is depending on which tank you enjoy doing more dps :>
For utility wise to help team, guardian,
Raids BDK
M+ Anything but not BDK
Good summary. 
But true.
Bear is auto pilot and Blood is rly fun. Both are equal imo. If you like looking at your character, go BDK
just healed a guardian and the dmg intake was very smooth. cant really comment on blood dks though.
@OP
Play Bear.
BDK is the most squishy tank in the game, and auto attacks can drop you to 40% life really quick.
Even as a druid lover, I can only advice you to go DK.
Bears are the most boring tanks, whilst BDK’s got a whole variety of abilities and their gameplay is much less braindead. People call them fragile because they don’t know how to play them properly, although they perform a bit less well than the rest of tanks.
^
Go bear blayy!
DROOD! Dk’s makes your healer suffer by taking too much damage, DROOD has the support of regenerating alot of health & increasing healing done by ze healer!
By growling at them!? 
By existing
and yes
Not in raids!
I don’t raid I only do M+ casually - So my comment below is for M+
Seriously I played with my Guardian recently.
It feels so amazing compared to BDK when it comes to damage intake. Healers are not complaining at all. While playing with BDK your life swings like a pendulum, it drives healers crazy.
Then I went through his kit. He can render few M+ affix USELESS! Which is huge advantage!
He can render Nercotic useless thanks to to Ursol’s Vortext and his mobility.
He can Sooth Enrage affix
He can also spec Typhoon in Sanguine weeks,
He has Incapacitating Roar which is an AOE disorient every 30 sec !! Very good!
And ofcourse the utilities he has like BR, Stampeding roars, etc!
His gameplay is not brain dead like what they are saying here, if you play it right. IMO the only tank spec that is brain dead is BRM but that’s different subject.
BDK cannot compete with these kit. Especially after 8,1 when they nerfed our AMS and made necrotic bypass it. In fact in some weeks many packs are totally scary for BDK if your Bonestorm is in Cooldown.
Don’t get me wrong, I looooove my DK, getting 100+K heals feels so amazing as a tank, but if you want Survivability BDK is not for you, because it can go down really quickly if you do not pay attention.
True but do you want to raid only for the rest of your life? #DROODGANG
From what ive seen as a non tank player, BDK’s are not too great lately.
I think bears more enjoyable. I don’t like the aspect of being a bear but you probably don’t mind it, which is a turn off from Druid for me.
On the other hand I really enjoy the looks and theme of BDK yet the spec puts me to sleep.
Enjoyment is then most important aspect, and I think you’d find that with Guardian.
Love how its all dks saying go bear XD. But yes go bear (coming from a healer)
I was about to say join the bear gang but that just doesnt sound right
I play every tanking class and I agree that guardian is not brain dead simple.
The utilities you described about guardian is true. but DK also have its unique advantage, death grip, mass grip, DnD aoe slow are just as good as guardian utilities if not better. They are the main reasons that BDK was so popular during BFA season 1 mythic+
Guardian lost “infected wound” which was aoe slow applied by swipe. I think it was the biggest nerf to guardian, which make kiting harder that it used to be.
Guardian’s advantage is swipe and moonfire has no cost and no cooldown. You can do range pull and aoe aggro without any downtime.
BDK’s real problem is SLOW speed. It is the slowest tank, real wheelchair class. I guess that is the reason why they are out of favor in current fast paced Mythic+.
PS: I agree that BrM is the real brain dead tank. Druid’s ironfur at least has rage cost and need to be managed. Ironskin brew is just a boring button you need to remember to press every few seconds. They might as well just make ironskin brew passive.