This debate, much like the caliber debate, will be a never ending one
In all honesty there is NO one way that is perfect for everyone. The choice you make wrt having a weapon mounted light or using only a hand held should be based on your situational circumstances. In my mind these should include, but are not limited to:
1. Laws in your state, county, city...
2. Personal situation i.e do you have kids, spouse that works a different shift or anything that could lead to a friendly making the bump in the night.
3. Probably the most important in TRAINING. With this I dont mean reading an article, book or watching a video, but actually doing training.
I consider having a weapon mounted light to be an advanced skill that people with no training should not use. You need to learn how to bounce light around the room so that you can see the "threat", not blind yourself (very important) and not cover the "threat" with your muzzle. If you are not able to do the training, youre safer using only a handheld. Violating one of the 4 rules in any situation is a BAD thing and if youre not properly trained it is VERY easy to simply point the muzzle at your preceived threat. Once you do this things can get VERY bad VERY quick.
You need to be able to balance speed with safety. In a competition speed is essential, but making a mistake only leads to a DQ. Making a mistake in life could lead to jail, or even worse living with the knowledge that you killed your wife, child...
i guess the jist is that we should use the tools that are appropriate to our skill level and stretch those skills on the range not the home.