Of these, I'd definitely go with Naomi. Unique letter pattern and sound, and usable pretty much around the world (it has a separate Japanese etymology, along with the Hebrew origin more familiar to the West).
Rebecca is a good, strong name, nothing objectionable. Becky has been memed to death, though, so Becca is the nickname I'd go for if I used Rebecca.
Sarah is pretty, but overused. I prefer the Sara spelling anyway.
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