The IQ is more similar than different. According to TDP, the RF version is slightly sharper in the corners wide open over the entire focal length range, but I haven't noticed much of a difference in practice. When using it at f/2.8, I'm not too concerned about corner performance. Stopped down, the differences go away. I will note that the RF is slightly better than the EF resolution-wise over more of the frame than at other focal lengths (you can see it at TDP) and that is my experience as well. When using EF, I preferred the 70-200 at 70 to the 24-70 at 70mm. With RF, I don't have much of a preference as to which lens to use at 70mm.
In practice, the real advantages of the RF version is that it has IS and doesn't require an adapter. For your use cases, IS isn't a critical feature. I would say that the R is more of a limiting factor for focus tracking/frame rate more than the ability of the RF/EF lenses to perform. So is the RF worth the difference in price? If you have other holes in your lens lineup, I'd suggest filling those first. If you're happy with your lineup and want to switch to the RF, then go for it.