R5 is about $400 more than a7rIV. But is R5 more functional than a7rIV?
The Sony is great for people needing 61MP over anything else, it is also smaller and lighter.
But for video, the Canon is incomparably more powerful. It a hybrid camera rather than a stills camera with some video capabilties.
It has a faster CFExpress card option to fully utilise all those features (if necessary).
It also has a much better quality rotating screen that is fully touch-compatible.
The IBIS is probably much better as well.
It also shoots faster at 12fps or 20fps with the electronic shutter.
The body is more spaced out with a top LCD as well.
We don't know how good the AF is, it is probably at least as good as the A7RIV (but not close to the A9II)
There are a good deal of features that the R5 offers for all that extra cash.