You didn't mention what your gleason score was and what percentage of cancer your one positive core was. As you probably already know gleason scores of 6 or less are less aggressive tumors while gleason scores of 7-10 are more aggressive tumors and more likely to spread.
As to your options , surgery versus radiation, the ten year survival is the same. Surgery is more likely to cause impotency and urinary incontinence from the get go, while radiation seems to initally have much lower rates of these complications but higher bowel incontinence immediately. 3 years down the road I think the potency levels for the 2 approaches is the same since radiation can eventually damage the nerves. You may ask what is the risk at your age of having permanent impotency? Probably about 50/50. Permanent incontinence probably a lot less than that.
Each approach obviously has risks and depending what side effect you are most willing to live with may determine your decision. Some guys are so scared about never having sex again go with radiation, while others who just want to get rid of the cancer go with surgery. One thing to remember is that if the cancer reoccurs and your PSA starts rising after either radiation or surgery you can't really go back and have surgery then. There is a procedure called salvage prostatectomy done by a few md's but it has a very high complication rate including development of fistulas with repeated repair surgeries. A few guys on this board talk about it and it ain't pleasant. So if the cancer comes back you have to move on to the third level of prostate ca treatment, anti-hormonal treatment and then the fourth level becomes chemo.
There are other treatments you might consider, like proton therapy, HIFU, and cryo. These treatments have less sideeffects than than surgery or radiation, but the long term effectiveness of these treatments is still not clear. Of course if you have a low gleason score cancer with low amount of cancer in your one core you could just do watchful waiting, where you have repeat PSA's and biopsies every few months to see if your cancer is growing very fast or not. Some cancers go nowhere, of course nobody really knows which ones do or don't. I didn't want to take that chance.
I am 52, had PSA rise from 1.9 to 2.85 in one year, negative DRE, second biopsy showed ca in 2/12 cores on R side, 5% cancer one core, 25% other core, clinincal stage T1c. Both had gleason scores of 3+3=6. Both of my parents died of cancer, I am very scared of cancer. Had bilateral nerve sparing robotic prostatectomy on 09/11/08. Pathological stage was T2a, organ contained, no signs of spread (so far!). Both post-op PSA tests have been less than .01. I was continent in 3 months but the ED remains. I have to have penile injections to have sex . I am very unhappy about the result of the ED, due to my age I felt I had shot of getting this back but it doesn't look like that's going to happen. I would do the same thing over again due to my paranoia about cancer but others choose different options based upon what they want to live with the rest of their life........prostate ca survivor