[craigjb]

Neither tool has a good way to do matched-impedance traces. Both rely on scripting or a plugin to do this, and the feedback is not real-time nor can you make design rules on matched nets.

Also, neither tool integrates smoothly with simulation software yet. One of my pet ideas for a while has been to integrate EEScheme, the KiCad schematic capture tool, with ngspice, an open-source spice engine. The integration would include things like probing voltages and currents in the schematic to make graphs appear. Or, associating spice models with library components.

However, this would also require some way to create "simulation-only" versions of schematics. Typically, you only want to simulate a sub-section of the schematic at once. No other schematic tool, even the big ones (Cadence, Mentor), does this very well yet.