I feel Atherys textures go along with each other better then Conquests. Also Atherys block textures are like the Default textures, but way better textured. Conquests, some if it's block textures are to far off the original texturepack, which makes if you build a cool structure in Conquest, it might look horrible in Default. Compared to if you would build something cool in Atherys, it would still look good when switching to Default. Which as a builder is my main priority, making it look good for everyone.
But both are good packs, I switch between them sometimes, but I much prefer Atherys ^^