From what I've heard and read (and seen demonstrated on YT), servo motors have excellent speed control and are much quieter than the typical clutch motor.
I have one industrial (Adler Class 98 zig-zag) and it's currently rated at 2200 but can achieve 3000 with a different pulley attachment (that I don't have), this with the Mitsu clutch currently installed. It seems fast but the actual clutch is worn, meaning there isn't much speed control so this is undoubtedly influencing my perception.
A truly fast machine means work is done very quickly. It also means mistakes are made very quickly. Were I making draperies or working with larger amounts of upholstery, I'm putting the pedal to the metal. And I would think feeding scraps through a 7000 SPM machine just to see what happens would be fun. Making a pair of boxer shorts? Not so much.