I always buy the new Note every year, passing the prev gen to my wife, and she passes her gen to my son... who, by that time is anxiously awaiting the replacement because he smashes up the screen, and/or destroys it entirely.
This makes the decision process easy for me.
That said, while I was completely happy with my N9, I am finding the differences to be substantial for my usage. I am power business user, and general product enthusiast as well.
The most notable for me:
1. Battery(wear and recharge) - I'm having a hard time wearing it down. It seems to actually get me through my day, and then some. This is helping me reduce the amount of extra batteries when on travel, and im more confident that I dont need to nurse the phone, or have alternative charging strategies. If I do get caught in a pinch, the 25w charger is very robust. These two differences really remove the legacy of battery headaches that i experienced on previous notes(and mobile phones in general).
2. Display - Im finding the extra little difference in screen size to be helpful when working with excel, general document review, and note taking. Its not that Note9 was poor in this respect, but the incremental difference is noticable when used for these purposes.
N10+ also is noticeably brighter. It pretty much checks the completion box of perfect brightness in full sun. Even when not in full sun, its powerful enough to get through my polarized sun glasses.
3. The rear accessory charge - I using this to charge my Frontier, and Samsung Buds. That wonky shaped watch charger is now banished from my travel kit.... Victory! Charging these devices anecdotally seems to draw very little from the battery.
On the more personal side, the wide angle lens provides and great photography flavor, and the video stabilization, and audio zoom is excellent.
Lastly, Storage, its fast and large. This will be my first note (aside from N5) that I have no plans to fuss with an external card.
To me the improvements on N10+ are not just incremental, but significant.
Regarding the perceived and popular nuisances are mostly a non-issue. Especially due to pairing with the watch.
HR sensor - rarley used, better served on watch
O2 - I always found this to be a gimmick
In screen finger print latency - I use smartlock with the watch, so i I only use FP for Samsung pay... not a big deal
Aux out - I use Samsung buds, but always keep wired headsets in my pack for back up. I have replaced those with the included USBC headset, which btw actually sounds impressively good. I do have some older audio cans, and at some point ill just buy a dongle for them.
I would like to see Samsung keep the jack and heart rate sensor on the next S11 series, but I believe that it will not happen unfortunately, which s u c k s. The last best S series. They shouldn't change anything with the S series. Keep the changes to the Note series, to make it a little different.
Me i like my S9Plus and i will keep it until he will die and if i have to change a battery i will do it. Never have a trouble with it and sometimes i do a factory reset and again my S9Plus as revived and whit the Samsung DeX Pad it the best thing i ever had.
I wanted Note 10 as well but I think I will stick with Note 9 for now. Well few new samsung development (108MP sensor, new exynos chip and 5G being standard) that came out recently has really convinced me to wait for the next one.