With regard to the Mugen AIS, as has been mentioned, this system avoids the potential for 'hot air' several other systems experience, but I would still be concerned about the lack of a resonator; it's cold air, which is the benefit of the stock airbox, but the mugen duct might make the cone just as dirty as the downforce piece made the unifilter, and any high rpm resonance benefit would be lost, as you have still replaced the resonator with a different type of duct. It's superior to a downforce/cantrell duct and intake system, but is it superior to a OEM airbox, OEM resonator, and high flow unifilter? It would be interesting to dyno both setups head to head, to find out which results in more power.
The hatch duct system would be even more interesting (although perhaps cost prohibitive), as the hatch area would act as a sort of air chamber, perhaps allowing for a greater supply of available cold air, with less dirt getting to the filter, and instead being trapped between the hatch/engine cover. Still, I would expect only minimal gains from any kind of higher flow air filter, the important point is getting cold air, then making sure your filter doesn't become overly dirty in a short span of time, then perhaps any kind of resonanace effect.
