Which do you prefer and why??

I use an M3 so I prefer the barrel mounted way. This allows me to take the light off of the shotgun and use it on my rifle or pistol with rail. I've used dedicated Surefire lights on my shotgun and rifle before and they are nice but prefer versatility and the M3s cost less.

I have the Surefire 6 volt forend on my 870.  I don't need to take my light off and put it on another weapon.  The Surefire product seemlessly integrates the light into a part of the shotgun as opposed to adding another attachment.  Activating the light is as naturatl as grabbing the forend which is somethnig you are usually doing anyway.

Quoted: I have the Surefire 6 volt forend on my 870.  I don't need to take my light off and put it on another weapon.  The Surefire product seemlessly integrates the light into a part of the shotgun as opposed to adding another attachment.  Activating the light is as naturatl as grabbing the forend which is somethnig you are usually doing anyway.

Do you feel that the Surefire forend is more cumbersome? Can you get a GOOD grip on it?

I'll agree that the Surefire feels more like a natural part of the shotgun than just another add-on.

My experience with barrel/mag-tube mounted lights made me question their dependability.  Namely, one time I found that the clamp that held a flashlight onto the mag tube was pinching it so tightly that it was restricting the flow of shells down the tube.  Then, if you loosened it a little, it started to jar and move around from the recoil.  Considering the nature of why I have a HD shotgun, I didn't want to risk it...I shelled out the dough for the Surefire and haven't looked back.

I haven't tried a light that mounts to a rail system on my shotgun, simply because I don't want to buy a rail for my shotgun.

As far as gripping the Surefire forend, that's not a problem.  It has a naturally "grippy" rubber and some grooves and ridges that help out.  It's a little bulky, but not so much that you can't get your hand around it.  The only issue I might consider is that I can't but help accidentally pressing the touch pad on the right side of the forend with my fingertips everytime I pick the gun up.  Not a big concern to me, but if you were aiming for stealth, a 1/5th second blast of light might give you away.

As stated above by others... I do not find the SF forend too bulky or difficult to manipulate and my hands are not particularly large.

I decided on a dedicated forend when I get the money for mine.  Especially for a pump, a barrel mounted light wouldn't work for me.  I don't want a constant on light, and it would be a bit difficult to keep using the pressure switch, a tape switch would have to be mounted to the forend, and that would mean a very long cord so it was long enough to work the action.
A rail directly on the forend and a tape switch would be ok, but that also would add more bulk.  A semi auto would work with a rail or barrel mount with now problem IMO.

Now I do like the ida of only having one light that I could switch between different guns.  That would save money, since I wouldn't need more than one light, and it's not like I'm going to be shooting more than one gun at a time. So maybe the rail on the forend isn't such a bad thought.  Oh well, for me anyway I have time to decide (in other words, too poor to worry about it now anyway.)