Re: Important query
The Super 3 is thicker and smoother, and louder. But the thing is, the Super Distortion is already thick and smooth. So the Super 3 is one of the least trebly bridge pickups available. The Super Distortion is good, but a little compressed. So if he ever wants that open, airy vintage sound, then the Tone Zone might be a better alternative. The TZ isn't really open or airy, but it can be more vintagey if it's backed away from the strings a little. The Evolution could also be a good choice to bridge the gap between metal and alternative. As for the neck, just make sure it's something versatile, like the PAF Pro, the Breed neck, or the Air Classic.
If you're going with Duncan, you can't lose with the Custom, or the Custom 5 in the bridge, and the Alnico II or '59 in the neck.