R.A.T.S. were released in Europe and Japan before the US Starriors release. The figures had different (more uniform) color schemes, and there were several vehicles that didn’t make it over here.
Starriors were released in 1984 in the US, after the first wave of (unnamed) Zoids came and went. They were robots, had windup weapons (either in their chest or right arm), and even had the little chrome pilot, but they weren’t Zoid-like in any other way.