Given what Art Morrison says about the diagonal links failing in street use, whether it's really true or not, I don't think you could go wrong with using the Panhard bar, just to be safe.
I saw reference somewhere about the diagonal links bending under cornering loads, if they're not beefy enough. They have to handle quite a bit more force than a Panhard due to the angle of installation. They may also somewhat hinder axle articulation, though that may be a disadvantage of 4-links in general.
