Well, depending on your tastes, MUCH better or a little worse!
It is much sharper and stays sharper and brighter in to the corners far better than the old 1.8, which I still have and will keep.
That said, I like the old 1.8 just for that reason. Shooting portraits, I like the way the old glass gets soft and dark in the corners.
But for everything else the RF is superior and the focus is faster.
But, honestly, I would reach for the new one 99% of time and maybe pull the old one out if I was shooting portrait of senior woman.
Sort of like a reaching for a Softar 1 by comparison!
The old glass was really nice at f4
This one is really nice all the way though. I am surprised how often I use it.
But it tanks out focusing indoors for video. the 24-105 is far superior for video but at 85, I would reach for the prime first.
i dont shoot much video, I actually hate video, but must shoot it for work at times, so that mean nothing to me, just mention for others who may like video.
It was $850 here in Canada and 45 for the hood!
I swear canon is extracting whatever they paid to the ransomware bandits by adding to the new gear. The 70-200 f4 is just over $300 more than Sony's.
If I lost it, would I buy it again?
YES
And I would still swear at Canon for the price of the lens and the fact the lens hood is $45 extra.
But, I would certainly replace it if I lost it.
Hope that helps a little,