Yes, I'd continue riding Dunn for now, although it's reassuring to have an Alou-caliber player on your bench in case one of those guys slips or gets hurt. For now, I'd definitely stick with Dunn; later in the season, you can rotate Pierre in and out, depending on whether you need steals or power, or simply exploit the Coors factor.
LOVE your outfield, by the way! (Ok, I may be just a tiny bit prejudiced, since I also have Sosa, Pierre and Dunn in one of my leagues...
