Dwarf racial is a convenient, on demand dispel/bleed removal. Increased crit damage is also very nice.
Dark Iron dwarf racial is a dps cooldown. Additional move speed indoors isnt noticeable with all the passive movespeed you can get from enchants/talents.
Dark Iron dwarf fire beard is superiour in every way and both heritage sets and unique.
Using other transmog options look exactly the same, minus the helms so you can still see an amazing fire beard.