"If you could choose a technology that prevents [1] 99.9% of issues in 100% of programs or [2] 100% of issues in 90% of programs, which one would you choose?"

Depends if I must use programs in the 10%

Assuming I can avoid that 10%, I would choose option [2] and select programs from amongst the 90% with zero issues

The problem I see with option [1] is that there would be no programs to select with zero issues

Over the 40 years I have been using software I have learned I do not need to use "100% of software"

I select a very small percentage of that 100%

I would not want to use most of that "100% of software", for various reasons having nothing to do with memory safety