S21 Ultra is my favorite phone from latest samsung. Love the form factor and feel in hand.
Disregard people who ask about exynos or snapdragon, real life difference is negligible unless you do all your work from phone. The phone will still work for a day, the photos will still be great, gaming is still also good, responsiveness will be top notch.
Why Ultra? Mainly because of cameras. You get full 0.6x, 1x, 3x, 10x system. The quality of photos still good and not much different from 22 and 23 Ultras, and I believe, they are better than non ultra 22 and 23. If you don’t use camera, the only big difference for you is size and design.
S22+ vs S23 is the same, the main difference is size and desing. Plus has quicker fast charging and bigger battery. Both phones have nice cameras with max 3x optical zoom. There are small improvements in s23, but they are not deal breakers.
Honestly, if s21 had 3x camera, it would still be a good device now. Latest generations have mostly incremental changes and new design.
From Ultra you will want to upgrade only to next Ultra, plus and non plus version just stop existing. And right now there is no enough reason to upgrade, unless the phone breaks. And if I got it correctly, common s23 is 1.5x more expensive than still good Ultra phone.
If I hadn’t totalled my S21U I’d still use it and be happy. Right now I’m using S22U, and the main difference is form factor, I didn’t feel any big improvements. Maybe, if they improve telephoto cameras on S24U, there will be reason to upgrade, but right now S21U is still pretty good premium phone.