Let me give my take on the "which tank brings what"-issue. First of all the usual background, I play a lvl80 DK Unholy Tank (Caritami), which as you'll see on the armory has a spec which will make plenty people frantically press CTRL+W to get the image out of their mind before it sears in (I have the permanent pet :P ). However, I have reasons for this spec and that is that I exclusively do 5man and 10man content on that character, and hence the pet is quite the nontrivial damage gain for the raid. I tried it with or without the talents, and this just worked better for me. Plus I like having the pet-feed ready at any given second.
That being said, my perspective for this is a mix of my own DK-perspective and my main being a shammyhealer who is usually assigned to tankheal.
I still value Druids for their overall consistency. More health, slightly higher reduction, Druids may strain your mana at times but they're extremely wall-ish in their tanking. They show nicely whether tank+healer gear is the issue because while they have plenty emergency options their strength does not come from those.
The "average" tank.
I learned Paladins as the tanks which produce insane threat - and in a way they kept that stigma. More so than that Paladins are the tanks for healers with bad reflexes as their damage slows when low on health + they have an extra life. For the actual numerical survival this usually means little but it allows healers a bit more slack as long as they manage to provide the raw output, and help the Paladin with external cooldowns since he only has a single controlled one.
The "relaxed but dependend" tank.
Warriors can be horrendously annoying to heal. They can easily zip around the battlefield to pick up adds or help people, but often this makes me engage the Nitro Boosters to try catch up before they die. Their damage intake seems on the low side on average, but is unstable due to the blocks + critical blocks. Any fight involving non-standard mechanics can usually make Warriors easier to heal due to them being able to bring their extra abilities to bear.
The "gadget" tank.
Share their spots with Warriors IMO, but without the unstable damage, but with more damage. It depends a lot on spec but I found that I can heal Death Knights comfortably as long as I can depend on them realizing the power of their utility moves. Death Knights I usually see survive the longest if shit hits the fan due to being able to counter so many attacks in some way or the other, but they do seem to suffer less wall-ish attributes in return.
The "oh shit" tank.
-- (The Death of Rats, Terry Pratchett, Soul Music)