I've been running a d5 for about 2 years and now I finally bought a DDC2 with a petras top.
However the DDC2 is the god of water cooling pumps. It significantly outperforms the DDC3.2 however it did have a much higher failure rate. Nearly 5%.
Found a gently used one and will report back on how it performs.
Also despite the D5's claimed higher flow rate the DDC has much more pressure when paired with an aftermarket top which will cause it to get better flow rates in a real world loop and not a free flowing one.
Use this to figure out what your flow in GPM would be with each pump, then make your decision.
Martin's Flow Rate Estimator