I had robotic surgery here in France a year ago. I have no idea what the process is called but it sounds rather like the DaVinci. They've been doing robotic prostrate surgery here for a very long time now. I was home 3 days after the surgery. On my bike less 3 weeks later but only for short rides but mostly because my legs were tired. Same saddle as before, a Selle Anatomica, zero problems at all with the saddle and riding.
Regarding the nuclear seeds and surgery, the explanation between the two that my surgeon gave me was that with surgery, if some cancer cells had already escaped the prostrate membrane and weren't removed during the surgery, they then follow-up with radiation therapy or something like that. The problem with the seeds is that they do not necessarily work on all the cancer cells yet there is no way of telling if that is the case or not. If for whatever reason the radiation didn't kill all the cancer, they are not able to then attack the remaining cells with surgery. I don't know why. Hence for me the choice was pretty clear, surgery first and then if needed, radiation, which hasn't been necessary. Also with the robotic surgery that I had, the prostrate is removed intact and then examined to see exactly how much cancer there was, where it was located, and what are the chances that some cells escaped.