Being logical Oakbeams, active surveillance is clearly the choice with the least side effects. Just a few appointments for ongoing monitoring.
But if you are an anxious type, you may find that more stressful than having an active intervention. And sooner or later (it could be soon or quite a few years) you may well find yourself needing treatment anyway.
Unfortunately, having treatment does mean side effects. You can read about them in the Toolkit booklets, but ultimately no one can say definitively what side effects you personally will get. Like a lot of things in life, you have to take a decision about the future without knowing what that future is.
My take is, surgery is a bit more of a high stakes gamble. Some people recover completely, others have longstanding problems with continence or erectile function (or both). Radiotherapy should allow more subsequent normality, but with hanging over you the worry that the radiation might trigger other cancers which could be a problem in 20+ years time (that is why it is easer to recommend in older patients). With both there will be issues of some sorts around the period of treatment.
Both have apparently similar probabilities of recurrence. After surgery PSA should have dropped to zero so any recurrence can be dealt with sooner and thus more effectively, and salvage radiotherapy following surgery is standard while surgery is often not (for technical reasons) an option after radiotherapy.
I have now experienced both, having had salvage radiotherapy recently following surgery six years before. I am happy to share my personal experiences if that is helpful - but that is just me, there seems to be quite a wide variation in how different men respond to treatment so you may end up different.