Clois,
I have built and driven both pan-hard and watts link axel locators. The pan-hard bar is definitely easier and cheaper to fabricate. However, there is a difference in how the car handles. The roll center on the axel side of the bar is constant. The roll center on the chassis side “floats” based on body roll. When you set up the bar, you adjust it to be parallel to the ground. In this position, the roll center is the same, when you turn the car (in the direction that causes the body to rotate about the chassis end of the bar) the body roll causes the chassis end, attachment point to dip, making it lower than the axle side. The result is different handling characteristics in left and right turns.
A watts-link has the roll center “fixed” about the center pivot point. It never changes left to right.
IMO, If you were building a combination street/track car with packaging and budget limitations. I would agree with the P-bar.
If you are going for track records, go with a Watts-link.
I don’t know what type of four link you run, but I have had excellent results with torque arms. They can really help put the power down coming out of the turns.
If your in the “buy” vs. “build” mode, I recommend Griggs Racing in Sonoma, Ca. They have a tremendous experience and a long winning history with stick axels.
http://www.griggsracing.com/
Jason