Hi Dave, I am another who would have looked at that 5 session radio with no HT as a very attractive alternative.
As you say, the possibility of salvage RT if PSA rises after surgery is a case for surgery, as is the very sensitive detection of recurrence since PSA should be zero once you don't have a prostate.
But it is a personal decision and you also need to think about side effects. Surgery takes the cancer right out (if everything works and they were right about no spread) but creates a risk of ongoing problems with urinary continence and erectile function - and there will certainly be short term issues. Radio will again have short term effects but functions should largely recover, but there is a long term risk of raised cancer risk in the bladder and colon, and no one enjoys the hormone therapy which has previously been involved. While 5 session RT is too new to have longterm follow up the most modern RT machines should minimise radiation spillover to adjacent organs and I would hope those risks are now less than in the published studies (if you think about it, any study with 10 year follow up has to have used older technology). Your age makes a difference, if you are under 60 you will more likely have good recovery from the trauma of surgery and a theoretical risk 20 years hence is a bigger issue.
There isn't a right answer, you just need to decide what you are happy with yourself. The PCUK resources are very helpful and there are nurses to talk to if that helps.