The different between ART and SRT are not small when adding AHT. But adjuvant therapy does not help everybody. From my personal experience I went from a 50% relapse rate at year 5 to remission today for five years. Can I attribute that to the decision for adjuvant therapy? I dunno. But it likely didn't hurt.
I mentioned this before but this was a tough decision that I made several years ago and my decision was based on bad science. I could find plenty of data by not doing adjuvant therapies and I did not like the results I was seeing. For me at age 44 at the time, I wanted better results and the unknown appeared to be a better option. I did see some data on ART with AHT and hitting the lymphatic system, and it looked very good.
I think that the difference between ART and SRT were minimal when the RO wasn't hitting nodes during the ART procedure. But WPRT has changed things quite a bit. If I were to do prostate cancer over, it would be the same as I have done it so far. I had an opportunity to consider adjuvant chemotherapy which I declined. But after five years of this stuff, I would have tolerated it well and could have missed another opportunity.
If I were in your shoes I'd get more opinions on the adjuvant radiation from another RO...
Advanced Prostate Cancer at age 44 (I am 49 now)
pT3b,N0,Mx (original PSA was 19.8) EPE, PM, SVI. Gleason 4+3=7
Da Vinci Surgery ~ 2/16/2007
Adjuvant Radiation Therapy ~ IMRT Completed 8/07
Adjuvant Hormone Therapy ~ 28 months on Casodex and Lupron.