[GuyBFF]

It's the way they made the DD Cube, not necessarily bad.
BE modified theres so the flow splits threw 4 - 5 pass rads (which makes constriction less, flow slower threw rad, yet shorter time to cool).
It just takes a little bigger pump to make the Danger Den work as it stays one tube all the way threw 15 passes. May work better as water has had 15 fast moving passes to cool, or maybe BE better as water has 4x5 slow moving passes. I haven't tried both.
I use a DD Cube as it's smaller and fits (and I use the bigger pump to get flow speed back up to good speed). Remember, all these pumps rated at 1', there usually less than one quarter there rated speed once in a system.
Overall Rad by Rad BE Aquacoil size makes it 1 C cooler, and those heater core types 1 C more (unless peltier, a little better)