not my experience at all.
koralia: quieter (not that the tunze are loud. I cant hear them either unless I'm right over the tank but I cant hear the koralias at all), cheaper, superior wider dispersed flow pattern (with attachment off)
tunze: better power to size ratio, superior mounting and aimability (I cant aim a Koralia where my tunze 6025 is without mounting it on a viewing panel while the tunze is on the backwall pointing 45deg from the mount), several known easy shroud mods to improve/alter performance, better looking.