Keep 'em both! It sounds nice actually, to have your original “look how far we’ve come”-rings. Maybe you could have a jeweller take a look at them, and make something that slots together or something like that?
Seeing as no documents are filed then renewals are done, there isn’t any way to track if divorce rates are higher or lower. Everyone can cite antidotal experiences, renewals because of a troubled marriage, renewal because the marriage is so great, etc…
My guess is that folks who renew their vows are more romantic and are less likely to divorce, but I’m just guessing.
In my case, it was both.