The ViewFinity S8 has a matte coating and I presume Samsung will use the same for the S9 and I don't think there has been any great outcry about the S8's matte coating.
I would prefer glossy since that is what I have been used to for almost a decade with my iMac 5Ks, but I need the ability to support multiple inputs (I will be using it with a Mac mini and a Windows PC) and that means the S9 is my only real option since the UltraFine and Apple Studio Display only have one input and I would therefore have to unplug the cable from either machine when I want to use the monitor with the other.
I would prefer glossy since that is what I have been used to for almost a decade with my iMac 5Ks, but I need the ability to support multiple inputs (I will be using it with a Mac mini and a Windows PC) and that means the S9 is my only real option since the UltraFine and Apple Studio Display only have one input and I would therefore have to unplug the cable from either machine when I want to use the monitor with the other.