I ran across this with my RS parlor. I tried normal tension strings and it was if the guitar opened up--better projection and sweeter tone. I'm not sure how this can be explained, but I have a theory.

I've noticed that as I move to harder tensioned strings the sound becomes increasingly steel-like and looses the warmth of nylon--the harder I strum or pick the more metallic the sound. I don't think that normal tension strings really project better, but I think I can play the normal tension strings harder and still retain warmth.

Not sure if all that makes sense. What is clear is that new materials, builds, strings, and so forth are leading to a different kind of guitar, one still in process.