Flashlights are really useful for finding out if the person in your house is an attacker or your kid coming home unannounced.
The main disadvantage of a handheld light is it makes it very hard to get a proper 2 hand grip. The main disadvantage of a weapon mounted light is your gun is pointed wherever you point the flashlight. The main advantage to each is overcoming the other's disadvantage.
My home solution is to use both, I have a compact handheld light with a wrist lanyard, and a TLR mounted on my nightstand gun. This allows me to use the handheld light to locate and identify, and the mounted option if I need light during any shooting.
The lanyard allows me to let go of the handheld light, so I can reload, clear malfunctions, grip the gun, or do any other required action with my left hand, and not lose the light.
It should be noted a good flashlight can be a weapon in and of itself, both as an impact tool, and just by impairing your attacker's vision.
As for giving away your position, that is a concern, but it gives away the position you were in when you used the light.
If you use momentary, and infrequent flashes only as necessary and move quickly the instant the light is off, this can largely be mitigated.
I like night sights on my defensive guns, but also recognize their limitations. They will let you line up the sights, but they don't let you identify your target. Also in darkness if you light up your target enough to ID them, the night sights aren't useful.
That said they are an advantage in low light.
Whatever you choose for your defensive gun, practice with them in low-light and darkness.
My suggestion for that is check with local competitions, one of the IDPA clubs I shoot at from time to time does a night match every year in November.
You shoot 6 or more stages starting after the sun sets using ambient light, a flashlight, or both.
They run standard IDPA divisions, and an outlaw mounted light division. So far I've only shot the handheld, and it made things interesting, but gave me several chances to use the light and gun while I was focusing on something other than using the light or gun.
I know other clubs around the country have similar matches, and it's a really good way to get some practice running a gun in the dark.