As I described for @Fred-on-Tarmac, the performance difference really depends on the type of riding you do and, thus, whether you can take advantage of such difference (and afford the cost difference).
In my case, as I do “spirited” group rides and road races (pre- and post- Covid), if there were such differences I wanted to understand them. The LBS that I buy my bikes from (largest NorCal Specialized dealer) let me take the Tarmac Pro and S-Works each out for a full day (actually I had them longer). I did simulated race testing, including: standing start accelerations, max watt efforts on open road (600-900), hill climbs (8-18%), cornering and descents with sharp turns. As I use TP Premium & WKO5, i did a comparative analysis of results where applicable and recorded several qualitative experiences for each ride as well. The differences between the bikes were very clear to me and I was able to afford the price difference (it was a special treat 
) such that I made the S-Works purchase. To this day (1.5 years on the bike), I still love the bike and am glad I made the decision that I did. But I do understand those that can’t afford or can’t justify the price difference.