Welcome to the forum!
- Not sure about your first question, can you give more detail? Some people like the Sapphire, most prefer the Hesalite
- The Pro has a bigger case than the FOIS (wider case with crown guards), so basically more metal, plus bracelet rather than leather.
- The FOIS is a Moonwatch, as in it is a later development of the Speedmaster, like the ones NASA used. This particular model has not been on the moon. Three references have actually been on the moon. These are very sought after.
https://www.fratellowatches.com/three-omega-speedmaster-references-that-were-worn-on-the-moon/
https://www.hodinkee.com/articles/comparing-moonwatches
I have A FOIS and a Pro (Hesalite), the Pro is my choice for a daily wearer.
Hope that helps
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