No, no, no. Nobody cares where the brass ejects to, just that it ejects, reliably.
What we DO care about is sight return. You're looking for the spring that has the front sight (or dot) returning to the same spot (your POA) after the recoil.
For my particular setup (Shadow 1, RTS2), bullet and load, and grip/shooting style, a 11# works best. With a regular iron sight, it was 10#.
You have to try different combos to find out what works for you (and that may change over time). Good luck!