Find a place where you can shoot at night. And take somebody who has been trained to search and shoot at night if you can.
Try controlling recoil using FBI, Harries, and Rogers holds with a handheld light.
Then experiment with a gun-mounted light.
Shoot some standardized drills. Measure splits and accuracy with each method.
Try shooting with your night sights.
Learn how to search with a flashlight. (Light on, search in one direction only for two seconds, light off, MOVE! etc.) Even how to use the switch matters.
Learn to perform administrative tasks (chamber check, unload, tac reload, clear malfunctions, etc. in the dark).
The advantages and disadvantages of each will become apparent. And then you'll know for sure what works best for you.
Learning to fight at night is FAR more involved than just deciding "handheld or pistol-mounted?"
+ 1
I've taken several low-light defensive shooting classes, handgun and long gun. In addition we occasionally shoot low light IDPA stages (Hand held only), and I get to shoot low-light at my place. I've trained and practiced the common HH techniques. Note that several; Harries, Rogers, place the light parallel to the bore, so that light might as well be mounted as far as risk of sweeping goes. Neck Index, puts the light next to your head, and does nothing to aid aiming ad recoil mitigation. FBI, while keeping the light away from you, also does nothing to aid shooting, nor recoil mitigation.
For HH techniques:
IF I'm searching I like Harries, because it's quick to disengage the flashlight.
IF I know I'm going to shoot, like in a stage, I like Roger's because it's better for recoil management.
IF I have my druthers, my light will be mounted. It's like cheating.
Modern tactical lights have a lot of "spill" and can be used to ID things at the "low ready" without sweeping.
My HD guns wear mounted lights, have HH lights stored with them, and I carry HH lights with my CCW pistol.
I believe there is such thing as too much of a good thing for HD, when it comes to lumens and around 300-500 is fine for indoors. You'll get bounce back as it is with every shiny surface you hit.
My advice mirrors above, take a class and learn how to use a light.