I'd take Harper but McCutchen is fine too. Both 5 tool guys and both would be great keystones to build your dynasty around. Harper plays in a better line-up so I give him the nod. That and he is younger.
I'd never take a pitcher first. It's about the position players first last and foremost from my pov. Pitchers arms are way to fragile and Strasberg already has a serious injury once. There is plenty of value in SP deep into the draft. And there are always the "next big thing" in pitching on the horizon.