Great choice. I love the concept of a watch ageing with the owner.
The 43 is huge and heavy. I’ve 6.75 wrists and no, too big for me. Your 16600 looks perfect.
You should go for both ;)
I have a 5 digit Sub and a SD43. Both are great in their own right. I don't find the SD43 wears big and it is comfy (once the divers extension is removed). I also wear a Pam so nothing is large compared to that :)