I personally am wondering the same question. I would expect H75 to be better since it's newer. From what I can gather, pump is important because some are noisy and radiator thickness. All of the round ones are supposedly Asetek design and all of the square ones are coolIT. From what I ve heard, asetek pumps are better (and less noisy). As for the radiator, the more surface you have for heat exchange the better. The length is more important than the thickness, besides with thinner radiator you can fit another fan on top (in some cases like my FT03 mini) therefore better cooling. With regards to fans? I have no idea.