Maybe it's the other ingredients in mixes I have used, but soils with vermiculite seem to be like sponges, and soils with perlite seem to dry out much faster. ??[background=rgb(255, 244, 228)]perlite does hold water. its porous as all hell. it may not hold as much as verm, idk.[/background]
I use an equal mix of both.
Perlite and Vermiculite are great amendments that do different things... using both of them in combination is by far better than using either exclusively, as they are not really comparable except for basic properties of water retantion and the fact that they take up space in a soil mix. A much better topic for comparison would be peat moss vs coconut coir, as they actually occupy the same niche in a soil mix.
While they both have similar porosity perlite generally has higher permeability so water and air flows easier in and out of it hence why most gardeners generally prefer perlite for an aeration material and vermiculite is preferred as a propagation material because it holds water for longer