Whats the best distortion pedal for a Metallica like tone in your opinion?

The pedals that I have been looking at our the Metal Muff and the Rocktron Silver Dragon. I have a Metal Zone currently, but it's not really doing it for me anymore, wana start looking at other options.

What do you think?

-Jackson DXMG (SH-2N, SH-6)
-Schecter Hellraiser C1 (18v)
-Ibanez XPT707FX (Blackouts)
-Ibanez BTB 400 Bass

Main Amp: Mesa DR Roadster