My understanding was that they call Sins a "RT4X game," rather than calling it just RTS. So in other words it has much more developed economic, political, diplomatic stuff instead of just a focus on combat. AI War is more like SupCom or AoEIII, except more complex in many ways. So it's simpler than a 4X (or RT4X) game, but probably more complex in the deep strategy than your average RTS game.