Shibumi, the Koralia 3 would probably be my pick of the two. It looks more sleek uses a tad bit less wattage and I did try the #4 and it was pretty strong. I like that the Koralia pumps are really flexible and u can position them just about anywhere... JMO
markandkristen, I have two 6045's and they are crap. Thank goodness I didnt spend money on them. The little clips that snap the pump into the magnets broke while in my tank... and not to mention the little flow they put out and they claim they are 1179gph...
Shibumi, the Koralia 4's compared to the Tunze 6045's push alot more flow, and thats from my experience, putting them side by side in the sink filled with water.
The reason I kept to the Tunzes were their sleek look, the Koralias look alot bigger.