Whatever your choice, it's reasonably still going to require familiarization and practice on your part.
You need to review available information from sources you consider trustworthy and credible, and then make your own informed decision.
Night sights may be very useful for aligning your handgun on an identified intended target under many reduced/low light conditions. Night sights have even been found by some folks to be useful when used with both hand-held and weapon-mounted light sources.
Flashlights are very useful for illuminating an area to identify things.
Flashlights can break, especially if dropped (under stress). Some are more robust than others in this regard. Dropping a light source may create more stress, reduce your ability to identify what's occurring in an area, and force unwanted multi-tasking to occur (fumbling with a dropped light while holding a firearm, and doing so while under potentially already stressful conditions.)
The potential for hand confusion to occur, especially under stress, is something to consider. Training and frequent practice can help.
Illuminating things with a weapon-mounted light means you're pointing your weapon at things, and likely before you've identified them ... under stress.
Weapon-mounted lights can fail, just like other flashlights. The shock of being unintentionally struck against something may be a bit different than the shock experienced during recoil. If you think you can't easily & unintentionally hit a weapon-mounted light against something while negotiating rooms inside a structure, you may be in for learning the same lessons learned by some SWAT & Patrol cops when first becoming accustomed to using weapon-mounted lights.
The method used to operate the weapon-mounted light should be carefully considered by each potential user. The circumstances under which a user anticipates using any particular system should be carefully considered. Potential hand confusion and training issues come to mind ... (for example, how do you feel about using a weapon-mounted light which requires your index/trigger finger to operate the switch ... under stress?)
When we first started issuing new pistols equipped with night sights (and equipment rails, FWIW), I remember hearing how surprised some folks were when they discovered that even when using a hand held flashlight to illuminate a potential target under low light conditions, the backlit night sights were even easier to see than standard sights.
I wasn't particularly in favor of night sights for many years. I finally realized the inherent potential advantages of night sights, even when used in conjunction with hand held flashlights. Both of my issued pistols are equipped with night sights, as are several of my personally owned pistols.
While I'm not particularly in favor of weapon-mounted lights for
my daily duties and tasks, I own and carry various styles, sizes and types of hand held lights ... and practice with them.
Can't offer the right answer for your needs ... only my own.