Well... I don't think this thing is new but at least it's new to me, I never see this trailer before and most of the MH3U HD trailer that post on youtube are in a very bad quality but you can hear them shouting HDHDHDHD version every freaking second.
I gotta say though, after watching that trailer, I'm totally gonna buy Wii-U for this game.
:) 1080i uses interlaced and 1080p uses progressive to display images on screen. While viewing 1080i you will see picture overlap from time to time, while it won't happen in 1080p. You can say that 1080p are smoother and much more vivid than 1080i.
You can look deeper into this at this website: http://hometheater.about.com/od/televisionbasics/qt/1080ivs1080p.htm