The irony that the same people consistantly increase their post count by seeking out threads in which they can cry 'search harder'
My preffered tuning is C#
Tuning isn't heavniess though, just for a start it's also to do with tone and the way in which the intruments are used in the song. An example I can think of is how Dimmu Borgir's "puritania" sounds far heavier than a song called 'into eternity' by splintered visions (or the other way round... I got the band from this forum as a suggestion of some arpreggios to learn
). Dimmu Borgir tune to E, and the other band right down to C. Another thing to consider would be how some Black Sabbath songs are in B tuning (as far as I remember, never had the interest to really verify it) but due to my preferences in tone and the somewhat sparse and empty recording mixes the band has, it doesn't sound that heavy. If you want a really clear illustration of this, just compare some Nile recordings to some Nile midi files, courtesy of the humble guitar pro
To me tuning down gives not only a better tone and sound for me, but also makes the instrument seem nicer to play, though this will be more due to the fact that my axe has been tuned down for years now so I'm used to it. It's a pain playing guitars in E in guitar shops etc.
Also it depends what kind of stuff you're going to associate the tones and tunings to I guess. Any riff based on the A string reminds me of the former days of metal, as do a lot of bands that tune to E and stick in the Aeolian modes, so despite the riffing it is unlikely to sound that hefty to me. Stick it into an approproate scale, such as the easy to grasp whole-half diminished and you're onto the beef despite your tunings.
Maybe it is a case of being sheepish, but as with evolution, if something works well there's little point in stubbornly ignoring it just for the sake of it. If you can be arsed to, tune down if you wanna play heavier stuff - you can always ride up a few frets and soon be back in the safety of standard tuning