It's not quite that simple. Changing to a too-lite hammer spring in a rough gun will cause light strikes, but changing to a moderately light hammer spring and a moderately light rebound spring in a smooth gun may not harm reliability and significantly lighten the trigger.
The idea is balance. Don't go too light and offset the lighter springs with some polishing and lubing (be careful here as well).
The GP100 I used to own was extremely light and smooth, but it took more than just springs to get there.
Chris