Originally Posted by Jakusonfire
The 35X produces more pressure than a D5/MCP655. Pressure produces flow relative to total restriction.
There is not a better or worse pump. Each has its strengths and weaknesses.
The 35X produces more pressure (at 1GPM about 6.4PSI) and is smaller. It can run a bit hot and many people use the heatsink with it. There have been instances of the 355 type pumps burning out.
The D5 (at 1GPM about 4.5PSI) is quieter and is cooled more effectively by water flowing through it
The loop you describe is not really a high restriction loop so either would be fine. The only Caveat is the Graphics card blocks ... AC blocks can be very high restriction compared to others.
That's a pretty succinct post. I would just add that both pumps make heat. It's just that one heats the air and one heats the water. You will be affected by both just the same. Some ppl like to pretend the D5 doesn't get hot but that is just rationale.
Another point is that the 35x will be able to expand with more blocks allowing you to maintain that 1-1.5 gpm ideal whereas a D5 will struggle necessitating an upgrade in pump later if your loop grows. In essence the higher head pressure capable pump will be more flexible down the line.