Zone is much easier to start in. In zone, you don't need a 150k gralat gun to compete with others. You don't need to constantly buy some item to allow you to respawn where you die instead of at a hospital on the other side of the map.
Yes, gameplay wise is easier to get into, the jobs are better mostly, you don't respawn on the other side of the map, but content wise Zone is falling behind. Sure there are bases, planets, and missions but the last big content update that is permanent that I can remember is when they revamped the shopping district or something like that.
Maybe the new tileset will add to its popularity by a bit but who knows when that will come, sometime this year maybe?