A lot of people recommend a D5 over the DDC pumps, but if you're dead set on a DDC then I'd recommend getting one with a heatsink. I personally don't see much of a difference between the two. The DDC, however, is known for overheating when not properly cooled (the PCB melts, pump breaks). Putting it in front of a fan usually prevents this.
As always, either of these pumps improve with a proper pump top, so those are also recommended.