LOL@used car salesman. Everyone has to believe their therapy is the best, I guess.
I don't agree with your urologist's assessment that they all have equal cure rates for intermediate risk PC. (They do for low risk PC). Most treatments use a measure called Biochemical Recurrence-Free Survival (bRFS) to give an indication of what the cure rate is. It tells you what % of men do not have an increase in PSA after a given period of time. For intermediate risk men, here are some comparative results at the best institutions (they are 5-yr bRFS rates unless otherwise noted):
Surgery - 77% (Dr. Hernandez et al. at Johns Hopkins)
Proton - 65% (Dr. Slater et al. at Loma Linda - among men with PSA 10-20)
SBRT - 93% (Dr. Katz et al. at 8 institutions)
SBRT - 99% (Dr. Meier et al. at 21 institutions, 3 year)
HDR brachy (monotherapy) - 94% (Dr. Rogers at GammaWest)
LDR brachy (monotherapy) - 97% ( Dr. Taira et al at UWSeattle)
IMRT (81 Gy) - 78% (Dr. Zelefsky et al at MSK, 8 years)
IMRT (86 Gy) - 86% (Dr. Spratt et al at MSK, 7 years)
Adding hormone therapy or a Brachytherapy boost may improve outcomes, but adding risk of additional side effects.
The reason that radiation generally has better cure rates than surgery for intermediate and high risk disease is because the radiation reaches into the prostate bed where cancer cells may have already migrated.
The side-effect profile of each therapy is different. With surgery, the risk of incontinence is high. A recent Duke U. study found 90% had some incontinence after 1 year. Only 37% of men have potency preserved even with nerve sparing, 13% without nerve sparing. Other common side effects of surgery include penile shrinkage, climacturia (urination at orgasm) and stress incontinence.
The various types of radiation have somewhat different side effects, but in general, urinary and rectal symptoms are mild and transient, reflecting irritation from the radiation. There is a transient peak acute effect soon after therapy, which may include getting up a few times at night to pee, some burning and maybe some diarrhea. All can be medicated if bothersome. The symptoms may recur a year or more later. Such late effects are generally transient as well. It's rare to experience any late effects after a couple of years.
In terms of potency preservation, here are the results I've found reported:
HDR brachy (Dr. Demanes) - 82%
CyberKnife (Dr. Katz) - 78%
IMRT w/o ADT (at MSK) - 65%
IMRT w/ADT (at MSK) - 46%
Seeds (at UWSeattle) - 56%
For protons, they don't report a comparable number, but only note that sexual dysfunction scores doubled after therapy.