I'm not sure about more weather resistant vs the chemically treated ones other than they're treated with heat to reduce the moisture content inside the wood to make it more resistant to rotting & fungus, our main reason was because we didn't want to expose Melody or ourselves with the chemically treated ones because we have a couple more critter related projects in mind. We basically just avoid any pallets that are painted green or some color on the edges, I know there's a specific and universal identifier stamp to tell the difference too :)