If you could choose one of these systems to be deterministic, which would you choose? What benefits/drawbacks do you see with each one?
Tempering you choose which temper you want with unlimited chances but masterworking remains as is.
Masterworking costs more materials and you choose what you want to have the crit on. You can reset it back to 0/12, 4/12, or 8/12 at anytime. Tempering remains as is.
Tempering would allow for builds to be changed on the fly and experiment with differing builds/skills.
Masterworking would have less clicking and my current build could be stronger with exact crits.
I see benefits to both sides but would ultimately choose tempering for the build diversity.