Does it matter which pan law I use?

It will always render as you hear it,  often better as some functions use "lower" quality algorithms during live playback and "high" quality for rendering.
 
Pan law affects how the volume of left/right channels change relative to each other when you turn the pan control.
You will only hear a difference if you change the pan law setting in preferences after you've already set pan controls on tracks.
 
 
As with a lot of settings, it doesn't actually matter which you choose as long as you're mixing with your ears and not your eyes.
 
Different brands of hardware analogue mixers use different pan laws as well.

Thanks for all the information. The article helped me out. It was good to see the actual levels in use.
 
Craig, thanks for the compliment. This is the name of my new black metal/industrial project, and I have no idea where the picture is originally from. Cerebus in cat form, but even google can't tell me who the artist is. The name alludes to my old handle on this forum, which was Resonant Order, a medieval term for octaves. I've always used Cakewalk products (all the way back to Pro Audio 5), but fell out of love with the X series. Decided to give the new subscription a shot (20.00? Sure, why not), and I'm using and abusing the program without any problems or crashes. Most of my complaints from before had to do with automation and vsti handling, and I can tell a huge difference in how Sonar works. I have yet to have a crash, motorboat (common with my Lynx drivers and Sonar in my experience), or error. I use it, and it works flawlessly, so I'm glad to be back. Viewing everything as a new start and very happy with where the program is at, the ideas planned for it, and the ability to use the subscription. With Slate coming on board with the subscription model, I feel that I'll want for nothing. That membrane between tweaking the gear and actual creativity continues to grow even more thin. Cheers!