You will find my discussion of blade edge at http://www.equipped.org/devices6.htm#SerrationsorSmoothEdge?
Bottom line is that a plain edge is more versatile and if you can have only one for all utility and survival use, that would be it. The serrated edge can be better at cutting nylon and such, so is preferred by rescue workers and most rescue knives have a serrated edge for this reasons, as they are cutting nylon seat belts and lines. You just need to decide what your primary objective is. The SwissTool has a serrated sheepsfoot blade if needed, so unless your primary need is rescue, I'd suggest the plain edge.