Ruconest has some distinct selling points. Because it is made from the milk of transgenic rabbits in a closed environment, there is not the risk of transmission of a human disease. The other treatments, Berinert, Firazyr, (Cinryze) are made from human blood, so they can contain infectious agents (eg, viruses and, theoretically, the Creutzfeldt-Jakob disease)
Patients don't seem to develop a resistance over time while this can be an issue with competitors. Moreover, Ruconest is approved for use ages 13 and up while Firazyr is only used 18 years and up.
Because Ruconest can be self administered, the IV/SQ issue does not really make a difference. What is really going to make the difference is if Ruconest gets the prophylaxis approval that they are working on. That would allow for use of the same drug for prophylaxis and acute attacks. I expect it will outsell the competitors all hands down at that point. Its also more effective for people who are overweight, that's at least a significant part of the potential users here in the States.