It is all very subjective.
I don't want anyone to take the following as fact, but it may be a cyclists prostate looks a little more battered than someone else's. One pathologist has seen loads of cyclist prostates and the other very few so they have different opinions on what a grade 3 really looks like. I really want to emphasize I have no knowledge of what prostates look like and this is just supposition to suggest why opinions may differ.
I don't know if you can get a third opinion, or whether it would be any more useful than the two prior ones.
I know with my locally advanced cancer no surgeon would have touched me. The chances of surgery working for me was as good as zero, so I would have made a dent in that surgeons statistics and also had an unnecessary procedure. If you have hardly any significant cancer you would have been very good for a surgeons statistics, and the procedure would be reasonable.
A breast cancer surgeon got 20 years prison for unnecessary operations. Such cases are very rare, but with a very low risk cancer you may look like sweet meat to someone with an eye on their statistics.
You haven't mentioned your PSA. I think if that is currently low maybe AS for at least six months may give you an idea whether your cancer is progressing. Viewing it as a stay of execution is probably quite right, but if you can put the date back 10 years you will have an extra decade of good life. If you put it back 20 years even better, but by then you will be less able to tolerate treatment (though by then treatment might just be one tablet of 'CancerCure patent medicine' available at all good pharmacies), if you push it back 30 years you will have died of something else before then anyway.