I had the old classic RT back in 2009, it was then just referred to as radiationtherapy, aka EBRT (External Beam Radiation Therapy).
It involved daily trips to the hospital over 4-5 weeks, and the problem was essentially controlling the side effects, the doctors said that killing off the cancer was no problem, the tricky bit of the treatment was not to kill off surrounding tissues in the bowels and bladder etc. Which in turn led them to limit the dosage of radiation therapy to the minimum they believed necessary to kill the cancer, and thereby minimise side effects.
The side effects were loose bowels etc and these tended to peak in the week or two following treatment.
Like most guys I was also on simultaneous HT (Hormone Therapy), it is known technically as adjuvant and neoadjuvant hormone therapy. The theory being that giving simultaneous HT maximised the effectiveness of the RT.
Feeling tired and lethargic are classic side effects of both RT and HT, so I didn't know which treatment was responsible for my ability to doze off in the afternoon.
In my case the cancer came back a couple of years after treatment. Whether this was because the initial treatment failed, or because as I was left with a functioning prostate, it developed a whle new tumour, is debatable.
Anyway I fitted the criteria for salvage treatment and last year had (HDR) High Dose Rate, Brachytherapy. This only involved two trips to hospital, all be it 3 day events with overnight stays. In theory because the radioactive probes are inserted into the tumour, then there is less risk of radiation effecting the surrounding tissues.
I found the side effects far easier, very little bowel problems and 3 months after treatment I was as right as rain. I then went on to suffer from a prostate infection and what I believe is called radiation cistitis, which were unplesant, but now almost 12 months after treatment, they seem to be sorted and I am well on the way to what might not exactly be a full recovery, but is better than it was.
Whilst all of this was going on the local support group was raising funds for our local hospital to buy its own HDR Brachytherapy kit. I understand (and I might be wrong) that the doctors believe that HDR brachytherapy is superior to EBRT and will ultimately become the default RT given to most all patients.
So best of luck in your deliberations, if I were in your shoes I would tend to choose HDR brachytherapy rather than EBRT, however as I have said I often get things wrong and there may be others who advise the opposite?