I would definitely go for the wrist. I gave up crack climbing when I got my flexnext on the back of the hand but I was more into parkour and bouldering than crack climbing anyway.
It’s more like bending it slightly hundreds of times until the solder joints start to peel off rather that break in the way you imagine it.
Sidenote:
I was an idiot and went climbing in the week following my flexnext install. Turns out the chalk(or tape?) gave me a pretty nasty rash on the whole surface of the implant. (I assume because the skin was weakened and some sort of parasite got in there). It went away with a bunch of creams but keep that in mind when healing, climbing gyms are nasty 