just figured out,
i use -3 constant power
 
 

ok, technically, according to Sonar, it is this:
 
-3dB center, sin/cos taper, constant power. 
This choice causes no boost in a signal that’s panned hard left or right, and 3dB dip in output level in either channel when the signal is center panned.

Jeff Evans
Pan laws do come into effect when you are transferring a whole mix from DAW A to DAW B.  Faders can be easily matched but pan settings are more about setting by eye in combination with correct pan law.
 
How things pan and how well the phantom image smoothly moves across is very dependent on correct distance apart for your monitors, in relation to you.

This might indeed be an issue.
 
 
But aside from that, the truth is there is no magic here - a pan pot just adds a certain amount of gain to each channel based on it's position. Different pan laws just control how much gain gets added at any given position.
 
So for any fixed pan position you can always get identical results through a combination of pan position and fader adjustment regardless of the pan law being used. Period.
 
Where it makes a difference is when you move the pan pot. As Bit said, if you're automating panning this makes a difference. Or like Jeff seemed to be getting at, if when mixing it doesn't seem to move naturally when you're trying to place something, or if you have to adjust the fader afterwards every time you change the pan position.

There's laws for this? 
 
I have probably been breaking them...  just saying.
 
I record and work mainly with mono tracks. The only stereo tracks I work with come out of the black box that way.  Only a few are like that though.
 
In my mix, I simply work to achieve a balance of sound. I'll record 2 nearly identical acoustic tracks for example and pan them 100% opposite.  It gives a wide image to the mix. I generally place them low in the mix so that the width they impart is more ambiance than in your face wide.
 
What I do on one side, I try to balance on the other. If I have piano on the right I place a guitar or something on the left at the same distance. Much of the panning is closer to center than 100% one direction of the other.   I also layer the panning.... there might be something at 100% something else at 50% and something else at 20%.
 
Layered vox also get the wide treatment as do harmonies..... but always balanced.
 
I hope that's what you're discussing.

Guitarhacker
There's laws for this? ...........
I hope that's what you're discussing.

 
no, this is a whole 'nuther thing.
everyone should understand this,
ESPECIALLY if you do collabs.
 

i move pans all the time.
 
in fact, i use pans sometimes, instead of volume/fader changes.
 
it takes advantage of my personal choice of pan law, as described above in post #12
 

I think the only lime I bothered to adjust a Pan Law was for Adobe audition which just lowers the level of everything on the output when the pan is centered, screwing up the loudness of pre-recorded material.    I keep it at 0 centered. 
 
For all other DAW's -3db center sounds fine and consistent to me, I rarely need to adjust volume when panning mono tracks.   What I usually do it set the volume close, adjust the position where I want it, and then fine tune the levels.  If the position of the track is stationary and you are not switching DAWs with different setting, I would argue pan law doesn't really matter.