What are your opinions? I have a G19, but its an older 2nd gen frame without a rail to mount a light. I keep considering getting a newer model, so i can mount a light to it, but I hear some opinions that say just use a hand held light.  What do you think?

50/50 on opinions...I have a Glock light mounted to my G22 in bedside safe. I have the choice to use it or not. I also have two more lights at bedside. One issue with the mounted light is if you need to use the light to see than you have covered the person with your muzzle. Gun rule violation. Another way around this is to get a good light that lets you light up the night while the gun is in the ready/registered position. Read on....

I have an M3 light mounted on the upper handgaurd, offset right.

I'd get in mounted right to the bottom, square on if I had it to do over.

Serves my purpose.

I have the M6 Tactical Laser Light on my XD9 and absoultly love it.  It is just one less thing to mess with when you need it.  With the push of my thumb I have a very bright light and a laser on target.  Can't bet that!

Stupid question, but if you use a hand held light for night clearing in your house, what is the technique for opening a door? How do you keep the pistol trained on your potential threat, light illuminating where your looking, and have a free hand to open a door?

I have an M6 on my Beretta 92FS Vertec...but since I prefer my Sig-P220 for home defence, and it does not have a rail.  I used my Surefire G2.

 A hand held light gives you a lot of versatility. Remember, you don't have to shine the light directly on the target to see it. You just have to illuminate the area enough to see. The gun mounted lights have a some things about them you need to take into account.
 One is the retraining issue of how you will grip your weapon with the light in place. You need to keep the finger that actuates the light on the light switch so you will have to learn that.
 Second thing is the lights I have tried out have very small switches. Using them under stress is not as easy as just pressing the large pressure pad of say a Surefire shotgun mounted light. You can train to do anything, but operating that little button while jacked up on adrenaline may be a challenge.
 Third, if your light is on your weapon it is very easy to start using your gun as a flashlight. This can create a situation in which you are shining it around looking at things meaning you are now pointing a loaded weapon at those things whether you need to be or not.
  Another thing is the cost of the weapon mounted lights versus a handheld light. Weapon lights are expensive and holsters to accept a light fitted weapon are another expense.
 Lastly, if you come up against someone who is serious he will shoot at the light. This is a big problem with weapon mounted lights since the light is right in front of you. IF the light is easy to turn on and off with gross motor skills you can light up a target, ID it, turn the light off and fire. The small buttons of the pistol lights make it tougher to do that.
 

I like the weapon mounted. I don't have to search for two things (gun and light) in the dark.

Bedside is a USP 45F + HK UTL. And yes... With my hands in a shooting grip, I can actuate the light switche/s.

Both are equally useable. The handheld light allows you to use multiple angles of light.  The weapon light allows you to keep both hands on the weapon, use one hand while illuminating something, etc.  

My wife has an H&K USP Compact .40 w/H&K UTL.  We both love it.  Yes, if I have to check something out I am covering it with the muzzle, but on the other hand, if I am checking out something that concerns me enough to make me take a firearm, that's an acceptable risk.  For all other situations, I'll get a standard flashlight.  Just my 2 cents.

Gus