With FDM, the fundamental limit (right now) is the viscosity and surface tension of the molten plastic. From memory, the Replicator 2 and the Ultimaker are hov

With FDM, the fundamental limit (right now) is the viscosity and surface tension of the molten plastic. From memory, the Replicator 2 and the Ultimaker are hovering around that limit - you can make smaller motions with the print head, but the feature size you get won't really benefit. With optical cure systems, in theory I think the limit is optical. In practice, there'll be unavoidable scattering at the focal point which will blur things a little, but I don't know exactly how much of a problem that is.