Current thinking is that DDCs using XSPC tops are reaching higher RPMs than those running EK/Petra/etc, causing higher power draw and early pump death. Those running higher restriction loops are safe, as the pump has more resistance to work against and therefore cannot reach such high impeller speeds and therefore cannot draw as much power. Non-XSPC tops are (it's thought) designed with a little more tolerance around the impeller, which results in slightly lower performance but slightly safer operation.