I am quite a strong advocate of getting the minimum treatment possible, to avoid the side effects.
One very strong consideration is how much longer do you expect to live. Another is how tolerable are the side effects. And of course, will this treatment cure the cancer or at least hold it under control until something else kills you.
Well at 69 you would hope for another 15 years of reasonable health. So the next question is will AS hold off this G3+4 T2a PSA9 cancer for 15 years or maybe 10 years and accept a small reduction in life length. The short answer is with some G4 present probably not.
If you were 80 and only expecting to live another five years, I would agree AS would be a good option, but at 69 with some G4. I think you need treatment.
Is HIFU possible? That has very few side effects.