I do know that the race of the tank in a party have little to non matter. But I realized one night I was playing that I relax a whole lot more then I heal Tauren, Orc and Blood Elf tanks. At least if they are warriors/druids/paladins.
I do NOT have a problem with troll or undead tanks. They just look so fragile with their tender limbs that I somehow feel I have to heal them a lot more than the big, cuddly tauren. I can’t imagine ever healing a gnome tank. I would go OOM instantly spamming heals on him even at 100% since I think he’ll be instantly crushed due to being so small. Dwarves are small too, but they look more sturdy than gnomes and night elves.
When it comes to blood elves I have gender issues. Male belfs look a bit sturdier than females. The female blood elf looks like the mere wind draft from a missed hit from a huge boss would knock them over.
So yes, late at night it feels so much safer having a big, safe tauren tanking than a skinny little catwalk belf girl.