When I was working for an automotive electronics supplier, we had all types of the depaneling equipment you have mentioned. Our strain studies showed that v-score (with straight blades) and routers induced the least amount of strain on components. The values were in the 100 - 200 micro strain area. Punch presses require vigilent maintenance to keep the sharp, clean and aligned. Punch presses averaged just below the 500 micro strain limit when maintained.

Based on our strain studies, v-score with straight blades was preferred for panels with straight cuts and router for irregular cuts. 

Cheers,

Brian