Heatpipes are usally filled with some amount of alcohol iirc.
Alcohol has a low boiling point. As the cpu heats up, all that heat energy gets spent boiling the alcohol (or whatever liquid).
Since it's gas form weighs less, the gas flows away from the liquid, to the other end of heatpipe, where it "dumps heat" into the fins and becomes liquid. Getting it back to the beginning is usually done with what everyone calls a "wick"
It's actually a very porous inner surface inside the heatpipe.
That porous surface perturbs air, thus slowing it down. This is why long heatpipes aren't necessarily better.
For very long heatpipes, the further the pipe is away from heat source (read: cpu) the less heat it gets from the gas inside, the less effective it is at the end.
So, in essence, long heatpipes aren't bad, as long as the fins start right where they leave the cpu's surface.
Also, cheaper heatpipes = less alcohol, or leaks, or possibly no liquid.
If it even is alcohol, don't take my word for it though.
This information brought to you by Necrofire, who did the few hours of internet research and cut a heatpipe open from curiosity.
Sweet coolers none the less, I'd take the all copper one though, that other one CAN'T be quiet.