Hi Ptr
Sorry to hear of your diagnosis, but welcome to the community.
Firstly I am total unqualified medically, but I was in about the same position as you are about five years ago Gleason 3+3 but a rather higher PSA with two separate tumors identified by template biopsy.
I was offered several treatment options including; external beam radiotherapy, Brachytherapy, radical prostatectomy by Da-Vinci, or HIFU. At that time HIFU was quite new and the probability of side effects was not well understood.
I elected to have Brachytherapy, as I was advised that with the position of my tumors this carried the lowest risk of impotence or incontinence. I was in hospital for only twelve hours, fully in control of by bladder within an hour of waking up. I was back at work within a week.
Regarding the more delicate subject of potency I found that with a lot of stimulation I could obtain an erection, but could not maintain it for long enough to do anything with it, I was prescribe a drug called "Tadalafil" also known as "Cialis"which has similar effects to "Viagra" but with the wonderful advantages that it becomes effective after only about 20 min. and remains effective for up to 48 hrs, so one dose on Friday night and you are good to go when ever it is appropriate for the whole weekend.
I really works, in fact I had as much vigor at sixty as i had in my thirties, the only remaining side effect was a reduction in the volume of ejaculate, but no loss of pleasure and less mess.
Unfortunately after four years clear of cancer I developed another tumor in a different part of the prostate, this is very unusual, but can occur after all treatments which do not total remove the prostate. As the tumor was quite aggressive Gleason 4+4 a radical prostatectomy was the only viable treatment.
I underwent a radical prostatectomy by Da-Vinci on March 18th 2015, six hours in theater, four days in hospital with a target of removing the catheter after five weeks and a return to work on lite duties after six weeks. I have been warned to expect urinary incontinence for up to twelve months, with a promise of further surgery to fit an artificial urinary sphincter if I am not in control after 12 months. Recovery time from surgery is longer after other forms of treatment as the blood flow to tissue is reduced by the scaring. As the nerve bundles had to be removed the prognosis for potency is poor, but there is some hope with the use of vacuum pumps and or injections you will find a lot of good information in the Prostate Cancer UK booklet "Prostate cancer and your sex life"
My personal experience is that Brachytherapy was no not much worse than the biopsy and a good option, and I understand that with an expert teem the outcomes are similar with HIFU.
Radical surgery is definitely a very major step with more risks of complications and a longer recovery time but with a greater probability of total permanent eradication of the cancer.
I was unlucky to get the cancer back but I have no regrets about taking the less invasive treatment option in the first instance, I have had four very good years, and still have hopes for the future.
Good luck for the future and let us know what you decide and .how you progress