Hmm, I always thought every tuning has its merits.... I only have one guitar currently, and it's tuned either in E standard or C# (though I prefer the latter). Okay, sometimes it's D as well.
Anyway - best sound in E? Hmm, I beg to differ
I'm FAR from being a sucker for downtuned stuff though. As far as my playing goes, anything lower than C# is too much.
Best sustain? Hmm, I always thought this had everything to do with string tension and nothing with pitch? I used to have Dean Markley heavy bottom (.010 - .052) strings on my guitar and sustain was great in C#. Better than it is now in E with standard .010 gauge. The only gripe with heavy bottoms for me is that you lose some of the attack, and that's why I don't use them any more.
As for the sound... hmm.
E standard is really great for old school stuff - with .010 strings it has that bright ring to it which I really like and I enjoy playing in it. It's not, however, MY sound, if you get the point.
E flat I've always regarded as an alternative for standard - the sound is practically the same, only the tension is a bit lower, which I like sometimes. And yeah... Slayer
D is really cool, it has an awesome growl to it and is my second favourite tuning. I'll go as far as saying it's the heaviest and most "brutal" of them all...
And now my favourite, C#. Usually with .010 strings. I don't know why, but this is my sweet spot. It has a very pleasing deep, dark timbre - majestic, almost monolithic... And the attack is very nice with .010s - just the right balance between tightness and that nice organic feel. Versatile - you can do thrash with it just as well as doom. Yup, I like it a lot.
Anything lower... bah. C is cool, but not as much as C#. B and lower is madness - for me, that is - on some records it sounds cool, but I don't like it at all. Unless it's a seven string, but even then... Nevermore are the only band who do it the way I like it.
To each his own, I guess...
