Have you ridden the flat base style boards yet? I am not a fan of them, but there are people that really enjoy them. The stiffenss of the Believer might be a bit much for a beginner so demo or rent one if you can. I like the Burton rocker/rev camber, and I like the way most of their boards handle. It would be my choice from the ones you listed for your skill level, but I haven't ridden the specific boards you listed. I am just making a recommendation based off what I know about the different styles of boards you are considering.
I like the Burton Custom and NS SL as mid-level/expert, do it all boards. I actually just finished researching this when my son wanted a new board that could do it all. Obviously no board is going to dominate backcountry, groomers and park at the same time, but these two boards were what we narrowed it down to. The NS won when "buysnow" had his size for $360 on sale.