This was taken with the A7RM4 and 135mm lens. It has been cropped to about 1/3 of its original size making up for the short tele focal length. Its no speed demon with often sluggish buffer but versatility and image quality make it all worth while.

OTOH my A9M2 is blazing fast and is capable of impossible sequences than that of the A7RM4. Its focus and tracking is a hair better and buffer is quite respectable. Its 24mp sensor is a weak point for my shooting, and that is why the 100-400 is on it most of the time.

They are obviously intended for different purposes. If I had to choose just one...either one would work just fine for me.