I am buying it a little.
They mount totally different though and have different characteristics.
To make sure we're talking "apples to apples"...

The panhard bar that can come with the kit mounts to the inside of the left frame rail, goes over the top of the differential, and mount directly onto the top side of the opposing side of the differential. On the front of the pumpkin itself (for this particular style).
The diagonal track bar starts at the back left connecting point of the 4 link and travels diagonally accross to the front right of the 4 link.

I definitely not a suspension engineer but, as I imagine (in my little pee brain) the movement of a vehicle turning, the force against and the allowable movement the two differents style would be very different.

1954 Chevy 3100 Panel Truck
2004 GMC Yukon
2002 Chevy 1500 4X4
"Those who expect to reap the blessings of freedom, must, like men, undergo the fatigues of supporting it."
Thomas Paine, The American Crisis, No. 4, September 11, 1777