I have both pumps, actually in my previous system i had both running in dual loops. The DDC is more practical to work with due to size and mounting options, but the D5 is noticeably more silent even at max setting (and properly decoupled). The D5 produces more vibrations though. A lot more. The DDC produces a semi-high frequency whine that is hard to block. Pump top choice was not a concern for me as both have EK tops.