Yeah none of it's really much use in practice. Motion ratios change as the suspension arms move, dampers determine how fast weight transfers, tires and wheels can change the track and/or have different levels of grip (not to mention affecting the spring rate!), etc. etc.

But theoretically speaking:
Roll rate is the more direct comparison of (static) handling bias, but looking at the equation you can see that roll rate is basically just wheel_rate*track^2.

Note that the (coil) springs also contribute to roll stiffness. The formula's the same except for a factor of 2:
U_spring = S_spring*(M_spring*K)^2*[pi/(2*12*180)]

Total roll rate for an axle is the sum of spring and bar roll rates, and overall roll rate for a car is the sum of front and rear roll rates.

 

springs F/R: 850/750
bars F/R: MY06/none
FU_spring = 1015.403 lb-ft/deg
FU_MY06_bar = 385.367 lb-ft/deg
RU_spring = 863.873 lb-ft/deg
RU_no_bar = 0

FU () = 1400.770 lb-ft/deg
RU = 863.873 lb-ft/deg
U = 2264.643 lb-ft/deg
FU/U = 62%

springs F/R: 850/750
bars F/R: Gendron (3rd hole)/MY06
FU_spring = 1015.403 lb-ft/deg
FU_Gendron_bar = 636.812 lb-ft/deg
RU_spring = 863.873 lb-ft/deg
RU_MY06_bar = 300.875 lb-ft/deg

FU = 1652.222 lb-ft/deg
RU = 1164.748 lb-ft/deg
U = 2816.969 lb-ft/deg
FU/U = 59%

[EDIT] Corrected math for RU.