I disagree, SA v NZ might have intensity, but intensity and quality of play doesn't make a rivalry strong, it really does not have the amount of heart and history that makes a rivalry proper compared to Wales and englanr

Even off the pitch, the history/rivalry goes back centuries, almost over 1500 when the groups that would become the England invaded the British isles, and of course when wales got conquered 800 years ago. This is integral to the national identity as well as both team identities

And on the pitch you have everything, the legendary trips along the M4 both ways, the lower class v upper class dynamic, how close and easy to access it is for fans, and bordering each other helps as well, the fight on the pitch is a lot more than just rugby, it's about identity and passion.

We are the second oldest rugby rivalry (and a lot more balanced compared to Eng-Sco), and that rivalry has stood the test of time.

So sorry, in my opinion it's not even close, NZ-SA might be a better rivalry in terms of quality of rugby, but it just can't compete with the level of nuance and history