I'll start this off by saying that I've never ridden in Japan- but I have ridden NS SLs many a time. I think the first one I rode was back in 1999 or 2000 (I can't remember, but the board was solid black except for a grey flame and a purple "SL"). I've been on a 2004 and a 2011 since. I currently have a NS Titan and 2010 Lib Banana Magic. In my experiences (and maybe I'm crazy) theres no way the Lib is stiffer. In almost every way the NS is more of an all mountain board to me- heavier, more stable at high speed, quicker initiation of turns. The banana magic is a ton of fun- but has a more playful, loose feeling to it. Also- it's definitely not built for Mike Olsen, that just doesn't make any sense to me. Overall I think both boards are great for overall riding- the lib is quite a bit more playful, and prob would be a little easier in the pow- the SL feels like more of a no nonsense all mountain board. Hope that helps!
Lib Tech Banana Magic/ Ride NRC
NS Titan/ Burton CFX