Stacked sensor BSI are the fastest reading sensors short of a true global shutter sensor.
Those that think it makes no difference have obviously never used a stacked sensor. Stacked sensors are the reasons those cameras can have insanely fast frames per second shooting, and with that much faster readout they have the best Tracking and AF performance.
Also fast reading stacked sensors greatly reduce the rolling shutter effect in electronic silent shutter when video shooting , and in electronic silent shutter in still shooting of fast moving subjects.
All huge benefits, and now the latest stacked sensors can also do flash sync in electronic silent shutter shooting, an industry first. NO other digital cameras sensors, BSI or not, can do flash sync in electronic silent shutter shooting.
Know the facts, and know why stacked BSI sensors are in the "flagship" fullframe mirrorless cameras from Sony (A1) , Nikon (Z9) and Canon (R3) , and in some cameras of smaller sensor sizes also.
Stacked sensors now exceed BSI CMOS sensors in focus speed, accuracy, and subject recognition. This all works together to ensure that stacked cameras don't just take a bunch of photos in a row; they take a bunch of in-focus photos in a row.
Another advantage that was made possible by the stacked sensor is the 'no blackout' or 'blackout free' EVFs.
You should look at this for a thorough explanation with illustrations.
"Why Stacked Sensor is the Future of the Camera Industry?"
https://techinspection.net/stacked-sensor-is-future-of-camera-industry/#:~:text=A%20standard%20CMOS%20sensor%20has,CMOS%20sensor%20contains%20multiple%20layers.
Know the facts ,and dont listen to folks here who commented and who obviously dont know the facts, LOL
I personally have owned two fullframe mirrorless cameras with stacked sensors, the 24mp Sony A9, and now the 50mp Sony A1. I reach for my stacked sensor A1 when I need all its stacked sensor advantages. I also have two fullframe cameras without stacked sensors, the 61mp Sony A7RIV, and the video-centric 12mp Sony A7SIII.
Cheers and best to you.