Ive used the Distortion a few times and recently got a Custom which I am loving.
I always thought the Distortion was very fat and fuzzy. Sometimes it can sound like it is going through a slight fuzz pedal all the time. It does sound nice, heavy, and aggressive, but I never really thought it was super tight. Ive always compared it to the Soulfly sound.
The Custom is tighter, clearer, and not as overloaded sounding. Its got low end chunk and high end clank. It sounds like the Megadeth Youthanasia sound to me. (I know they used a JB, but still....)