Priced at $1,599, the ViewFinity S9 has the same price tag as the Studio Display from Apple, but Apple charges an additional $300 for Nano-texture matte glass and $400 extra for a tilt and height adjustable stand.
A lot of Apple users feel the Studio Display's overpriced, so it's interesting that Samsung isn't competing on price.
If I were deciding between the two, and it didn't come down to unique features like portrait mode, then I'd want to see them side by side in a brightly lit room. The regular (non nano-texture) Studio Display handles most reflections decently well, but if the ViewFinity does much better then I can see that being a plus for an office setting where you have lights or windows behind you. I'm sure the nano-texture does better yet, but it has some trade-offs and cleaning requirements that make me very reluctant to recommend it. (I don't like that the wording above suggests nano-texture is a regular matte glass. It's not. It's better in many ways, but it's not for everyone.)