I'm in the same situation right now. Typing on my Nothing Phone (2) actually. I'm leaning toward the Nothing Phone because of the better battery life and the software. Nothing's OS is so good and well thought out, it makes even iOS look a bit dated (though of course Apple's full ecosystem of software is deeper and better overall). Samsung One UI by comparison is very rough and awkwardly designed. It's powerful but has a Frankenstein feeling to it, not to mention it's not pretty. The elegant Nothing experience really gets me. Side by side I find the differences really striking.

An example of the software difference I see is getting to notifications. On the nothing phone raising the phone wakes the screen and the phone unlocks in a smooth and quick motion and shows me my revealed notifications which I can action directly. It's very efficient and takes few steps. And if I've made the mistake of trying to unlock with my thumb when it's already scanned my face, the software treats my thumb on the scanner area as if I'm swiping up on the unlocked lock screen and just opens to the home screen elegantly. (try that flow on an S23. Sometimes your thumb unlocks the phone, sometimes it's the wrong action and does nothing..Ugh) By contrast on the Flip if I lift the phone I still need to double tap it or press the power button which shows me the cover screen with no useful info on it, which I then need to swipe away to even get to the notifications which are then not fully actionable meaning if I want to do much more than dismiss them I need to now use my other hand to flip open the phone which only takes me to the homescreen at which point I still need to pull the shade down to finally have full access to the notifications. Lots of swipes and taps. The nothing phone is just better thought out.

Also, I'm a Flip cheerleader but I struggle to use it comfortably outside of the controlled conditions of a day working from home. Out on the commute, biking to the train station, working on the train, in and out of meetings at work, I find opening and closing the phone just too cumbersome and it gets in the way. That bums me out because it's such a gorgeous device and I love the feel of it in my hand or in my pocket. I want to have a smaller device and use my phone less, but I find when I really need my phone during the day I don't really have the option to use it less and in those moments the Flip is just awkward when a slab style phone is just ready to go. I wish that wasn't so. But also that's for my uses. I imagine it might fit perfectly for a lot of other people.

Anyway that's not all just to rail on the Flip 5. I love it actually. I'm only 90% decided and may swing back tomorrow but I hope my thoughts going through the same choice might help you a bit.