I currently use both as well. As far as atmospheres, I dont think you can get those into Modo. You can, however, easily add lights and utilize GI to “fake” a standard atmosphere. Also, you can export any of Vue’s plant objects as an .obj or .lwo for import into Modo, but I guarantee there will be some cleanup required. Modo cant always find the correct texture maps.
So far the best workflow I have found is using Modo to model and texture, import into Vue, add atmosphere and ecosystem, render in Vue and finally touchup in Photoshop. Seems too work out the best with minimal hassle.