Like Ryat said. Most Multiplayer RTS is about whoever gets the most first wins. It's not just Sins, but pretty much every RTS. However in Single Player vs. the AI you can take as much time, "turtle, and porc" as much as you want, because the AI will "let you do it". Even Cruel, and Vicious cheating AI. I think that is where you get the "empire builder" feel. In MP you don't have much time to stop, and smell the roses.
I like the idea about a "Real Time Tactics" mode. You start with a finite amount of ships, and in battle you have to deal with what you got. Very "Total War-ish". I guess the flagship victory condition is as close as we can get for now.
I think though Sins is a hybrid 4X/RTS. It is more an RTS with just a little bit of 4X tossed in.