The Salsa frame is really really light scandium. Since it has the same modulus as regular aluminum, I would worry that it might be too flexy.
The Van Dessel (I keep wanting to say "Vin Diesel", wtf)... ermm... anyway it looks to be a little more suited for multiple seasons and/or clyde use. However, those carbon seatstays are getting about as faddish as purple anodized **** was a decade ago. Some manufacturers just bulk order pre-fab CF stays and throw them into frames without regard for whether it really makes the resulting frankenframe any better. In other words, overbuilt prefab CF stays may result in a heavier, flexier, less reliable bike. I don't know about Vin Diesel's frame to say what the deal is in this particular case though.
Voting for the Van Dessel, since my gut feeling is that the Salsa is a 1-season frame for greyhounds.