The big changes are about security and privacy when we are using the phone. The personalize are a few things. My opinion is samsung has incorporate the good lock stuff into a default settings to get a better performance for personalize de phone
Not major changes but...at least I notice more animations in many areas, more smoother, I began to notice them more when I put my phone a little bit more slow in the developer options .5X for sure Samsung will include more animations, maybe we like someones and other don't but...right now are a few YouTube videos of the pixel 6 and I have to say...Samsung is ahead in options and customization.
Samsung has always been ahead with options. You couldn't even have a bold font on a Pixel phone until Android 12! Couldn't see the text onscreen without setting the font to ridiculous sizes. Come on Google - billions of people use your software.
We have to wait for Beta 3 first to get a conclusion. Everybody is talking about stock Android 12 on the Pixels and sincerely is not a big deal, Samsung One Ui 4 will be better; it has been always the case.