That is so cool that it changes to black. I bet it had a depth that is different than onyx. Both are beautiful and you should choose the one you think you would wear more often.I recently had a visit with an SA in Vegas and we spent most of the time playing with the letterwood. The wood will absolutely darken over time and become nearly black - one of the SAs was wearing a full set and it was almost as dark as onyx. I love the way it looks. Other than that she did not mention any other issues - I was looking at durability vs all pink gold.