I don't know anything about guitars in general, or strings either, for that matter, but I do know that my Martin sounds its best when tuned properly. I've tried to live with the slightly deteriorated tone when tuned down, because I have a low voice and often have to stretch, when in the keys I like to play in, to reach some of the notes. But it appears my voice is (slightly) more flexible than this guitar...and since I love to hear this guitar at it's best, I don't tune down. If I can ever afford another guitar, this will be one of the things I look for. Also, along the same lines, it seems to me that use of capo degrades the tone on some guitars...mine doesn't sound quite as good capo'd to A as it does played in A...seems to cinch the sound down a little, somehow, so it is not as full.