Importantly the precision means the orbit of JWST needed less fuel to correct, leaving more for future corrections and extending the lifetime.
> The launch was described by NASA as "flawless" and "perfect".[4] A NASA systems engineer said “the efficiency or the accuracy with which Ariane put us on orbit and our accuracy and effectiveness in implementing our mid-course corrections” meant that there is “quite a bit of fuel margin ... roughly speaking, it’s around 20 years of propellant.”[16][17]
From https://en.m.wikipedia.org/wiki/Ariane_flight_VA256
When you have many satellites and want it cheap, go with SpaceX. If you have one priceless irreplaceable satellite hundreds of people spent decades building, go with Ariane. There is market for both.