These are very different Cab Packs. One is a huge 4x12 with four speakers: 4x Mesa custom Vintage 30s (Cab Pack 13) and the other is three separate Zilla 2x12 cabinets (which sound and look amazing by the way) with six completely different tonal characters and pretty much unlimited options.Does it completely blow away cab pack 13? Or is it just different? I've been pretty happy with 13. But, I'm contemplating this. Especially since it includes presets.
If a new pack is really good it doesn't make the older packs any worse if that makes sense. That being said you can not get things even close to the tightness of the Zilla pack (especially the "D" IR's) with Cab Pack 13. These two packs are very different.
Check this video to get a glimpse of what the pack is capable of: