I own both, and its the Fold 5 hands down. S23U is an amazing phone, great camera and battery life. But its boring to me. Ive had almost every Note series type phone made, and once I switched to the Fold 3 a few years ago, ill never go back to slab phones.
You hear about people scared about the screen cracking, just get good protection from your carrier or Samsung when you buy it. Ive personally never had a single issue with any of the Folds. Most of the people that crack their screen just didnt take care of it.
You will also hear complaints about the front screen being small. For me, the front screen are just for quick tasks. Check a message or an email, make a phone call, do a quick search, etc. If im actually going to use my phone for entertainment, its opened to full screen all the time. And its amazing.
The camera on the Fold 5 might not be as awesome as the S23U, but for me its solid. Ive never had any issues for normal everyday use. Pictures look great.
But ultimately, it comes down to personal choices. Id recommend going to a store where you can get hands on both, and see which one feels right for you.
I had the Flip 3 and Flip 4, and returned them both. They were really cool, but battery life and camera were subpar for me.
As I said in my post, ive had the Fold 3, 4, and now 5, and loved them all. Just go somewhere you can get your hands on one, and take it for a test drive.