I think there are a few misunderstands with the FPS and many are to do with personal preferences
Lets face it if we were in the wild west shoot out with our phones on our hips the S9's/Note 9 would leave your opponent long dead as by the time you have grabbed your S9 and got as far as waist high it's on and unlocked and firing where say the Iphone your still raising it to your face
Maybe a slightly unreal scenario but it does translate to those that carry phones in their trouser/pants pocket or handbag/purse
Similarly if you want an unlocked sneak peek at your phone under the table or in your purse it's a thumbs up for FPS over face recognition
For those that use their phones on or in bikes cars etc maybe there more pro's to front FPS's over rear FPS or FR
Of course FR excels for those occasions when say your wearing gloves and it's security is one of the best, but it's not always about security as FR is on so few laptops for example and none on MBP/Airs etc
. FR also is fractional more convenient for in app use and maybe where Samsung should of kept Iris Scan
Then there is the whole table top usage argument where front FPS is more advantageous
However I think we are seeing some mixed feedback hear, ignoring screen protectors and update
The new under screen FPS is suppose to be more secure so until muscle memory kicks in the comparison on touch/feel to old FPS will seem different
Maybe the added security currently interferes with reliability and a software tweak will improve this or it's just part of the S10's learning curve as it does seem to improve over a day or so but that could be more the user than the phone
The added security can also make some digit prints easier or harder to recognise, I certainly see a difference between my index finger that's almost instant on a light touch where my thumb needs slightly more pressure to get the same results.
That's not the S10's fault it's just picking up my imperfections LOL
Of course ex Iphone FR owners may find the transition to FPS differently but you have to look at your usage pattern on how you first hold your phone from pocket, purse, table etc and the single on and unlock
I think many will be surprised how trivial comparisons are, FR is and is more of a deliminator on branding than an outright advantage for many.
FPS are likely to cover more scenarios for most but at times FR is nicer