I voted Tube, because you said Tone! If you would've asked, "Which amp is better for playing Heavy Metal?" I would surely have voted Solid State, but as far as pure tone goes, tube has the tone. But, like TJ said, each amp is it's own entity, and in the end will make as big a difference (if not a bigger difference) as what type of guitar you use. Some tube amps are built more for playing the heavy stuff, but solid state + overdrive is hard to touch for playing metal. Of course, my experience playing tube amps is reserved to Fender Blues Deluxe and Twin Reverb and whatnot, so the "tone" is definitely there, but when I try to fuzzbust it up it turns into cacophony. I'm sure the Marshall JVM would totally convince me that tube is the way to go, forever. Speaking of Marshall JVM, anyone got $1800 I can have?
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Every one of us has heard the call
Brothers of True Metal, proud and standing tall
We know the power within us has brought us to this hall
There's magic in the metal; there's magic is us all